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	$110.48	5.665%	$116.7387	$116.74	$116.75	$116.70
Purchase #2	$178.64	7.575%	$192.172	$192.17	$192.15	$192.20
Purchase #3	$50.61	12.375%	$56.873	$56.87	$56.85	$56.90
Purchase #4	$131.48	12.311%	$147.6665	$147.67	$147.65	$147.70
Purchase #5	$238.64	7.642%	$256.8769	$256.88	$256.90	$256.90
Purchase #6	$62.37	6.810%	$66.6174	$66.62	$66.60	$66.60
Purchase #7	$224.48	6.165%	$238.3192	$238.32	$238.30	$238.30
7 purchase totals =	$996.70		$1,075.2637	$1,075.27	$1,075.20	$1,075.30