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	$142.83	6.167%	$151.6383	$151.64	$151.65	$151.60
Purchase #2	$152.34	4.520%	$159.2258	$159.23	$159.25	$159.20
Purchase #3	$79.83	12.145%	$89.5254	$89.53	$89.55	$89.50
Purchase #4	$180.81	11.498%	$201.5995	$201.60	$201.60	$201.60
Purchase #5	$104.90	6.235%	$111.4405	$111.44	$111.45	$111.40
Purchase #6	$39.35	3.249%	$40.6285	$40.63	$40.65	$40.60
Purchase #7	$237.57	7.170%	$254.6038	$254.60	$254.60	$254.60
7 purchase totals =	$937.63		$1,008.6618	$1,008.67	$1,008.75	$1,008.50