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	$169.30	7.326%	$181.7029	$181.70	$181.70	$181.70
Purchase #2	$110.95	11.107%	$123.2732	$123.27	$123.25	$123.30
Purchase #3	$53.50	5.185%	$56.274	$56.27	$56.25	$56.30
Purchase #4	$123.43	11.217%	$137.2751	$137.28	$137.30	$137.30
Purchase #5	$194.73	11.816%	$217.7393	$217.74	$217.75	$217.70
Purchase #6	$152.72	8.792%	$166.1471	$166.15	$166.15	$166.10
Purchase #7	$72.37	7.142%	$77.5387	$77.54	$77.55	$77.50
7 purchase totals =	$877.00		$959.9503	$959.95	$959.95	$959.90