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	$242.88	4.130%	$252.9109	$252.91	$252.90	$252.90
Purchase #2	$146.40	10.561%	$161.8613	$161.86	$161.85	$161.90
Purchase #3	$46.89	13.807%	$53.3641	$53.36	$53.35	$53.40
Purchase #4	$175.50	13.360%	$198.9468	$198.95	$198.95	$198.90
Purchase #5	$181.33	7.574%	$195.0639	$195.06	$195.05	$195.10
Purchase #6	$48.71	13.759%	$55.412	$55.41	$55.40	$55.40
Purchase #7	$59.95	10.599%	$66.3041	$66.30	$66.30	$66.30
7 purchase totals =	$901.66		$983.8631	$983.85	$983.80	$983.90