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	$219.39	7.229%	$235.2497	$235.25	$235.25	$235.20
Purchase #2	$15.94	7.731%	$17.1723	$17.17	$17.15	$17.20
Purchase #3	$156.32	10.112%	$172.1271	$172.13	$172.15	$172.10
Purchase #4	$99.42	9.656%	$109.02	$109.02	$109.00	$109.00
Purchase #5	$197.87	9.709%	$217.0812	$217.08	$217.10	$217.10
Purchase #6	$33.30	11.526%	$37.1382	$37.14	$37.15	$37.10
Purchase #7	$136.54	10.679%	$151.1211	$151.12	$151.10	$151.10
7 purchase totals =	$858.78		$938.9096	$938.91	$938.90	$938.80