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	$98.35	13.446%	$111.5741	$111.57	$111.55	$111.60
Purchase #2	$165.91	11.560%	$185.0892	$185.09	$185.10	$185.10
Purchase #3	$47.88	6.140%	$50.8198	$50.82	$50.80	$50.80
Purchase #4	$97.88	11.174%	$108.8171	$108.82	$108.80	$108.80
Purchase #5	$90.26	6.308%	$95.9536	$95.95	$95.95	$96.00
Purchase #6	$30.53	4.776%	$31.9881	$31.99	$32.00	$32.00
Purchase #7	$113.63	4.634%	$118.8956	$118.90	$118.90	$118.90
7 purchase totals =	$644.44		$703.1375	$703.14	$703.10	$703.20