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	$62.84	4.275%	$65.5264	$65.53	$65.55	$65.50
Purchase #2	$81.35	12.366%	$91.4097	$91.41	$91.40	$91.40
Purchase #3	$129.95	13.476%	$147.4621	$147.46	$147.45	$147.50
Purchase #4	$59.47	10.654%	$65.8059	$65.81	$65.80	$65.80
Purchase #5	$200.51	10.824%	$222.2132	$222.21	$222.20	$222.20
Purchase #6	$108.92	13.568%	$123.6983	$123.70	$123.70	$123.70
Purchase #7	$74.81	10.353%	$82.5551	$82.56	$82.55	$82.60
7 purchase totals =	$717.85		$798.6707	$798.68	$798.65	$798.70