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	$141.52	5.872%	$149.8301	$149.83	$149.85	$149.80
Purchase #2	$18.69	12.151%	$20.961	$20.96	$20.95	$21.00
Purchase #3	$130.88	9.760%	$143.6539	$143.65	$143.65	$143.70
Purchase #4	$36.37	5.181%	$38.2543	$38.25	$38.25	$38.30
Purchase #5	$137.50	10.772%	$152.3115	$152.31	$152.30	$152.30
Purchase #6	$32.51	9.265%	$35.5221	$35.52	$35.50	$35.50
Purchase #7	$102.64	10.153%	$113.061	$113.06	$113.05	$113.10
7 purchase totals =	$600.11		$653.5939	$653.58	$653.55	$653.70