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	$221.71	3.364%	$229.1683	$229.17	$229.15	$229.20
Purchase #2	$250.99	4.826%	$263.1028	$263.10	$263.10	$263.10
Purchase #3	$228.33	11.727%	$255.1063	$255.11	$255.10	$255.10
Purchase #4	$108.52	10.324%	$119.7236	$119.72	$119.70	$119.70
Purchase #5	$27.81	8.707%	$30.2314	$30.23	$30.25	$30.20
Purchase #6	$39.78	7.829%	$42.8944	$42.89	$42.90	$42.90
Purchase #7	$110.41	12.155%	$123.8303	$123.83	$123.85	$123.80
7 purchase totals =	$987.55		$1,064.0571	$1,064.05	$1,064.05	$1,064.00