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	$239.38	6.481%	$254.8942	$254.89	$254.90	$254.90
Purchase #2	$190.55	10.156%	$209.9023	$209.90	$209.90	$209.90
Purchase #3	$60.45	7.559%	$65.0194	$65.02	$65.00	$65.00
Purchase #4	$153.60	10.124%	$169.1505	$169.15	$169.15	$169.20
Purchase #5	$123.89	11.328%	$137.9243	$137.92	$137.90	$137.90
Purchase #6	$180.72	8.180%	$195.5029	$195.50	$195.50	$195.50
Purchase #7	$40.61	6.691%	$43.3272	$43.33	$43.35	$43.30
7 purchase totals =	$989.20		$1,075.7208	$1,075.71	$1,075.70	$1,075.70