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	$144.31	5.446%	$152.1691	$152.17	$152.15	$152.20
Purchase #2	$44.85	5.298%	$47.2262	$47.23	$47.25	$47.20
Purchase #3	$92.83	7.478%	$99.7718	$99.77	$99.75	$99.80
Purchase #4	$243.69	5.533%	$257.1734	$257.17	$257.15	$257.20
Purchase #5	$90.73	4.640%	$94.9399	$94.94	$94.95	$94.90
Purchase #6	$84.64	5.630%	$89.4052	$89.41	$89.40	$89.40
Purchase #7	$58.79	13.843%	$66.9283	$66.93	$66.95	$66.90
7 purchase totals =	$759.84		$807.6139	$807.62	$807.60	$807.60