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	$133.73	7.853%	$144.2318	$144.23	$144.25	$144.20
Purchase #2	$52.57	9.865%	$57.756	$57.76	$57.75	$57.80
Purchase #3	$99.56	9.190%	$108.7096	$108.71	$108.70	$108.70
Purchase #4	$131.52	12.435%	$147.8745	$147.87	$147.85	$147.90
Purchase #5	$19.96	7.523%	$21.4616	$21.46	$21.45	$21.50
Purchase #6	$141.47	8.822%	$153.9505	$153.95	$153.95	$154.00
Purchase #7	$80.34	11.670%	$89.7157	$89.72	$89.70	$89.70
7 purchase totals =	$659.15		$723.6997	$723.70	$723.65	$723.80