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	$124.53	5.288%	$131.1151	$131.12	$131.10	$131.10
Purchase #2	$66.31	7.428%	$71.2355	$71.24	$71.25	$71.20
Purchase #3	$175.86	5.603%	$185.7134	$185.71	$185.70	$185.70
Purchase #4	$65.89	9.605%	$72.2187	$72.22	$72.20	$72.20
Purchase #5	$88.55	11.804%	$99.0024	$99.00	$99.00	$99.00
Purchase #6	$31.97	8.439%	$34.6679	$34.67	$34.65	$34.70
Purchase #7	$102.55	7.236%	$109.9705	$109.97	$109.95	$110.00
7 purchase totals =	$655.66		$703.9235	$703.93	$703.85	$703.90