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	$94.97	12.157%	$106.5155	$106.52	$106.50	$106.50
Purchase #2	$90.47	4.184%	$94.2553	$94.26	$94.25	$94.30
Purchase #3	$48.25	4.616%	$50.4772	$50.48	$50.50	$50.50
Purchase #4	$150.29	6.570%	$160.1641	$160.16	$160.15	$160.20
Purchase #5	$150.49	12.554%	$169.3825	$169.38	$169.40	$169.40
Purchase #6	$65.26	10.406%	$72.051	$72.05	$72.05	$72.10
Purchase #7	$67.80	12.679%	$76.3964	$76.40	$76.40	$76.40
7 purchase totals =	$667.53		$729.2420	$729.25	$729.25	$729.40