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	$39.46	10.528%	$43.6143	$43.61	$43.60	$43.60
Purchase #2	$126.51	3.119%	$130.4558	$130.46	$130.45	$130.50
Purchase #3	$55.60	3.685%	$57.6489	$57.65	$57.65	$57.60
Purchase #4	$125.84	12.534%	$141.6128	$141.61	$141.60	$141.60
Purchase #5	$174.73	3.703%	$181.2003	$181.20	$181.20	$181.20
Purchase #6	$41.39	12.595%	$46.6031	$46.60	$46.60	$46.60
Purchase #7	$200.72	11.300%	$223.4014	$223.40	$223.40	$223.40
7 purchase totals =	$764.25		$824.5366	$824.53	$824.50	$824.50