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	$168.65	9.472%	$184.6245	$184.62	$184.60	$184.60
Purchase #2	$144.83	5.647%	$153.0086	$153.01	$153.00	$153.00
Purchase #3	$33.46	13.836%	$38.0895	$38.09	$38.10	$38.10
Purchase #4	$194.76	3.673%	$201.9135	$201.91	$201.90	$201.90
Purchase #5	$144.77	4.473%	$151.2456	$151.25	$151.25	$151.20
Purchase #6	$126.32	4.331%	$131.7909	$131.79	$131.80	$131.80
Purchase #7	$78.76	5.357%	$82.9792	$82.98	$83.00	$83.00
7 purchase totals =	$891.55		$943.6518	$943.65	$943.65	$943.60