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	$179.26	13.414%	$203.3059	$203.31	$203.30	$203.30
Purchase #2	$178.71	10.174%	$196.892	$196.89	$196.90	$196.90
Purchase #3	$39.60	7.358%	$42.5138	$42.51	$42.50	$42.50
Purchase #4	$198.69	11.658%	$221.8533	$221.85	$221.85	$221.90
Purchase #5	$141.52	8.344%	$153.3284	$153.33	$153.35	$153.30
Purchase #6	$86.37	9.105%	$94.234	$94.23	$94.25	$94.20
Purchase #7	$185.33	11.533%	$206.7041	$206.70	$206.70	$206.70
7 purchase totals =	$1,009.48		$1,118.8315	$1,118.82	$1,118.85	$1,118.80