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	$106.86	11.299%	$118.9341	$118.93	$118.95	$118.90
Purchase #2	$106.46	11.118%	$118.2962	$118.30	$118.30	$118.30
Purchase #3	$49.73	9.281%	$54.3454	$54.35	$54.35	$54.30
Purchase #4	$99.41	10.166%	$109.516	$109.52	$109.50	$109.50
Purchase #5	$30.93	13.386%	$35.0703	$35.07	$35.05	$35.10
Purchase #6	$95.57	13.248%	$108.2311	$108.23	$108.25	$108.20
Purchase #7	$203.76	9.104%	$222.3103	$222.31	$222.30	$222.30
7 purchase totals =	$692.72		$766.7034	$766.71	$766.70	$766.60