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	$80.71	13.330%	$91.4686	$91.47	$91.45	$91.50
Purchase #2	$243.81	4.724%	$255.3276	$255.33	$255.35	$255.30
Purchase #3	$161.67	6.333%	$171.9086	$171.91	$171.90	$171.90
Purchase #4	$54.62	11.800%	$61.0652	$61.07	$61.05	$61.10
Purchase #5	$34.71	8.155%	$37.5406	$37.54	$37.55	$37.50
Purchase #6	$225.86	11.220%	$251.2015	$251.20	$251.20	$251.20
Purchase #7	$161.83	4.390%	$168.9343	$168.93	$168.95	$168.90
7 purchase totals =	$963.21		$1,037.4464	$1,037.45	$1,037.45	$1,037.40