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	$165.89	13.673%	$188.5721	$188.57	$188.55	$188.60
Purchase #2	$132.57	12.413%	$149.0259	$149.03	$149.05	$149.00
Purchase #3	$119.74	8.141%	$129.488	$129.49	$129.50	$129.50
Purchase #4	$22.37	11.198%	$24.875	$24.88	$24.90	$24.90
Purchase #5	$228.48	12.305%	$256.5945	$256.59	$256.60	$256.60
Purchase #6	$189.98	4.466%	$198.4645	$198.46	$198.45	$198.50
Purchase #7	$101.56	7.469%	$109.1455	$109.15	$109.15	$109.10
7 purchase totals =	$960.59		$1,056.1655	$1,056.17	$1,056.20	$1,056.20