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	$248.83	6.365%	$264.668	$264.67	$264.65	$264.70
Purchase #2	$180.28	11.397%	$200.8265	$200.83	$200.85	$200.80
Purchase #3	$91.52	3.772%	$94.9721	$94.97	$94.95	$95.00
Purchase #4	$234.59	5.616%	$247.7646	$247.76	$247.75	$247.80
Purchase #5	$223.72	3.363%	$231.2437	$231.24	$231.25	$231.20
Purchase #6	$56.77	10.781%	$62.8904	$62.89	$62.90	$62.90
Purchase #7	$19.75	8.205%	$21.3705	$21.37	$21.35	$21.40
7 purchase totals =	$1,055.46		$1,123.7358	$1,123.73	$1,123.70	$1,123.80