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	$55.34	10.507%	$61.1546	$61.15	$61.15	$61.20
Purchase #2	$99.90	13.830%	$113.7162	$113.72	$113.70	$113.70
Purchase #3	$101.41	3.147%	$104.6014	$104.60	$104.60	$104.60
Purchase #4	$203.47	3.250%	$210.0828	$210.08	$210.10	$210.10
Purchase #5	$34.27	9.700%	$37.5942	$37.59	$37.60	$37.60
Purchase #6	$213.96	6.659%	$228.2076	$228.21	$228.20	$228.20
Purchase #7	$180.57	10.489%	$199.51	$199.51	$199.50	$199.50
7 purchase totals =	$888.92		$954.8668	$954.86	$954.85	$954.90