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	$90.47	11.161%	$100.5674	$100.57	$100.55	$100.60
Purchase #2	$156.28	10.652%	$172.9269	$172.93	$172.95	$172.90
Purchase #3	$147.25	4.225%	$153.4713	$153.47	$153.45	$153.50
Purchase #4	$97.29	8.744%	$105.797	$105.80	$105.80	$105.80
Purchase #5	$135.72	6.444%	$144.4658	$144.47	$144.45	$144.50
Purchase #6	$174.97	9.637%	$191.8319	$191.83	$191.85	$191.80
Purchase #7	$245.57	11.483%	$273.7688	$273.77	$273.75	$273.80
7 purchase totals =	$1,047.55		$1,142.8291	$1,142.84	$1,142.80	$1,142.90