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	$139.71	8.133%	$151.0726	$151.07	$151.05	$151.10
Purchase #2	$30.58	13.496%	$34.7071	$34.71	$34.70	$34.70
Purchase #3	$18.36	6.423%	$19.5393	$19.54	$19.55	$19.50
Purchase #4	$36.68	3.108%	$37.82	$37.82	$37.80	$37.80
Purchase #5	$98.48	7.551%	$105.9162	$105.92	$105.90	$105.90
Purchase #6	$12.92	4.792%	$13.5391	$13.54	$13.55	$13.50
Purchase #7	$249.83	7.145%	$267.6804	$267.68	$267.70	$267.70
7 purchase totals =	$586.56		$630.2747	$630.28	$630.25	$630.20