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	$101.76	8.221%	$110.1257	$110.13	$110.15	$110.10
Purchase #2	$136.92	11.738%	$152.9917	$152.99	$153.00	$153.00
Purchase #3	$248.92	13.745%	$283.1341	$283.13	$283.15	$283.10
Purchase #4	$167.54	12.666%	$188.7606	$188.76	$188.75	$188.80
Purchase #5	$88.98	12.872%	$100.4335	$100.43	$100.45	$100.40
Purchase #6	$78.92	3.387%	$81.593	$81.59	$81.60	$81.60
Purchase #7	$189.36	11.353%	$210.858	$210.86	$210.85	$210.90
7 purchase totals =	$1,012.40		$1,127.8966	$1,127.89	$1,127.95	$1,127.90