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	$47.45	6.205%	$50.3943	$50.39	$50.40	$50.40
Purchase #2	$88.47	10.715%	$97.9496	$97.95	$97.95	$97.90
Purchase #3	$188.50	3.625%	$195.3331	$195.33	$195.35	$195.30
Purchase #4	$218.37	13.431%	$247.6993	$247.70	$247.70	$247.70
Purchase #5	$133.84	12.439%	$150.4884	$150.49	$150.50	$150.50
Purchase #6	$210.78	9.852%	$231.546	$231.55	$231.55	$231.50
Purchase #7	$39.83	7.503%	$42.8184	$42.82	$42.80	$42.80
7 purchase totals =	$927.24		$1,016.2291	$1,016.23	$1,016.25	$1,016.10