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	$100.48	10.345%	$110.8747	$110.87	$110.85	$110.90
Purchase #2	$100.32	4.396%	$104.7301	$104.73	$104.75	$104.70
Purchase #3	$55.85	11.244%	$62.1298	$62.13	$62.15	$62.10
Purchase #4	$9.82	8.869%	$10.6909	$10.69	$10.70	$10.70
Purchase #5	$81.70	10.281%	$90.0996	$90.10	$90.10	$90.10
Purchase #6	$62.73	3.313%	$64.8082	$64.81	$64.80	$64.80
Purchase #7	$141.34	7.711%	$152.2387	$152.24	$152.25	$152.20
7 purchase totals =	$552.24		$595.5720	$595.57	$595.60	$595.50