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	$162.27	12.371%	$182.3444	$182.34	$182.35	$182.30
Purchase #2	$149.74	4.538%	$156.5352	$156.54	$156.55	$156.50
Purchase #3	$96.98	3.272%	$100.1532	$100.15	$100.15	$100.20
Purchase #4	$61.85	6.325%	$65.762	$65.76	$65.75	$65.80
Purchase #5	$50.62	7.688%	$54.5117	$54.51	$54.50	$54.50
Purchase #6	$5.70	13.437%	$6.4659	$6.47	$6.45	$6.50
Purchase #7	$90.99	7.521%	$97.8334	$97.83	$97.85	$97.80
7 purchase totals =	$618.15		$663.6058	$663.60	$663.60	$663.60