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	$33.28	12.456%	$37.4254	$37.43	$37.45	$37.40
Purchase #2	$54.75	12.646%	$61.6737	$61.67	$61.65	$61.70
Purchase #3	$159.46	13.665%	$181.2502	$181.25	$181.25	$181.30
Purchase #4	$94.53	12.332%	$106.1874	$106.19	$106.20	$106.20
Purchase #5	$12.61	10.105%	$13.8842	$13.88	$13.90	$13.90
Purchase #6	$48.30	4.818%	$50.6271	$50.63	$50.65	$50.60
Purchase #7	$35.50	3.820%	$36.8561	$36.86	$36.85	$36.90
7 purchase totals =	$438.43		$487.9041	$487.91	$487.95	$488.00