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	$220.86	6.322%	$234.8228	$234.82	$234.80	$234.80
Purchase #2	$94.26	12.596%	$106.133	$106.13	$106.15	$106.10
Purchase #3	$139.77	11.159%	$155.3669	$155.37	$155.35	$155.40
Purchase #4	$162.54	10.454%	$179.5319	$179.53	$179.55	$179.50
Purchase #5	$24.72	5.453%	$26.068	$26.07	$26.05	$26.10
Purchase #6	$172.74	6.817%	$184.5157	$184.52	$184.50	$184.50
Purchase #7	$122.72	6.765%	$131.022	$131.02	$131.00	$131.00
7 purchase totals =	$937.61		$1,017.4603	$1,017.46	$1,017.40	$1,017.40