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	$58.58	10.224%	$64.5692	$64.57	$64.55	$64.60
Purchase #2	$70.46	8.248%	$76.2715	$76.27	$76.25	$76.30
Purchase #3	$209.65	11.485%	$233.7283	$233.73	$233.75	$233.70
Purchase #4	$95.85	13.872%	$109.1463	$109.15	$109.15	$109.10
Purchase #5	$131.96	11.374%	$146.9691	$146.97	$146.95	$147.00
Purchase #6	$188.43	4.399%	$196.719	$196.72	$196.70	$196.70
Purchase #7	$41.95	11.688%	$46.8531	$46.85	$46.85	$46.90
7 purchase totals =	$796.88		$874.2565	$874.26	$874.20	$874.30