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	$52.33	9.813%	$57.4651	$57.47	$57.45	$57.50
Purchase #2	$171.95	9.446%	$188.1924	$188.19	$188.20	$188.20
Purchase #3	$230.93	10.159%	$254.3902	$254.39	$254.40	$254.40
Purchase #4	$212.88	3.864%	$221.1057	$221.11	$221.10	$221.10
Purchase #5	$176.62	13.638%	$200.7074	$200.71	$200.70	$200.70
Purchase #6	$97.93	13.667%	$111.3141	$111.31	$111.30	$111.30
Purchase #7	$41.30	4.660%	$43.2246	$43.22	$43.20	$43.20
7 purchase totals =	$983.94		$1,076.3995	$1,076.40	$1,076.35	$1,076.40