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	$188.29	12.539%	$211.8997	$211.90	$211.90	$211.90
Purchase #2	$204.89	12.287%	$230.0648	$230.06	$230.05	$230.10
Purchase #3	$174.85	6.787%	$186.7171	$186.72	$186.70	$186.70
Purchase #4	$37.31	7.136%	$39.9724	$39.97	$39.95	$40.00
Purchase #5	$167.47	6.574%	$178.4795	$178.48	$178.50	$178.50
Purchase #6	$66.64	8.743%	$72.4663	$72.47	$72.45	$72.50
Purchase #7	$170.57	11.495%	$190.177	$190.18	$190.20	$190.20
7 purchase totals =	$1,010.02		$1,109.7768	$1,109.78	$1,109.75	$1,109.90