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	$53.64	4.531%	$56.0704	$56.07	$56.05	$56.10
Purchase #2	$37.82	7.795%	$40.7681	$40.77	$40.75	$40.80
Purchase #3	$126.65	3.523%	$131.1119	$131.11	$131.10	$131.10
Purchase #4	$78.38	4.589%	$81.9769	$81.98	$82.00	$82.00
Purchase #5	$130.45	5.271%	$137.326	$137.33	$137.35	$137.30
Purchase #6	$134.57	13.215%	$152.3534	$152.35	$152.35	$152.40
Purchase #7	$91.74	13.556%	$104.1763	$104.18	$104.20	$104.20
7 purchase totals =	$653.25		$703.7830	$703.79	$703.80	$703.90