Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.70	12.842%	$190.3645	$190.36	$190.35	$190.40
Purchase #2	$151.51	13.630%	$172.1608	$172.16	$172.15	$172.20
Purchase #3	$105.85	11.426%	$117.9444	$117.94	$117.95	$117.90
Purchase #4	$115.42	13.511%	$131.0144	$131.01	$131.00	$131.00
Purchase #5	$220.83	6.576%	$235.3518	$235.35	$235.35	$235.40
Purchase #6	$156.85	6.661%	$167.2978	$167.30	$167.30	$167.30
Purchase #7	$144.75	4.158%	$150.7687	$150.77	$150.75	$150.80
7 purchase totals =	$1,063.91		$1,164.9024	$1,164.89	$1,164.85	$1,165.00