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	$133.92	9.597%	$146.7723	$146.77	$146.75	$146.80
Purchase #2	$82.36	8.356%	$89.242	$89.24	$89.25	$89.20
Purchase #3	$208.87	6.592%	$222.6387	$222.64	$222.65	$222.60
Purchase #4	$182.33	7.366%	$195.7604	$195.76	$195.75	$195.80
Purchase #5	$143.55	10.408%	$158.4907	$158.49	$158.50	$158.50
Purchase #6	$37.78	5.727%	$39.9437	$39.94	$39.95	$39.90
Purchase #7	$229.99	12.569%	$258.8974	$258.90	$258.90	$258.90
7 purchase totals =	$1,018.80		$1,111.7452	$1,111.74	$1,111.75	$1,111.70