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	$130.67	9.629%	$143.2522	$143.25	$143.25	$143.30
Purchase #2	$35.75	4.367%	$37.3112	$37.31	$37.30	$37.30
Purchase #3	$125.56	12.671%	$141.4697	$141.47	$141.45	$141.50
Purchase #4	$229.87	5.290%	$242.0301	$242.03	$242.05	$242.00
Purchase #5	$215.42	13.774%	$245.092	$245.09	$245.10	$245.10
Purchase #6	$222.44	9.212%	$242.9312	$242.93	$242.95	$242.90
Purchase #7	$140.57	12.434%	$158.0485	$158.05	$158.05	$158.00
7 purchase totals =	$1,100.28		$1,210.1349	$1,210.13	$1,210.15	$1,210.10