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	$132.80	9.280%	$145.1238	$145.12	$145.10	$145.10
Purchase #2	$227.44	12.873%	$256.7184	$256.72	$256.70	$256.70
Purchase #3	$42.50	7.120%	$45.526	$45.53	$45.55	$45.50
Purchase #4	$42.28	6.694%	$45.1102	$45.11	$45.10	$45.10
Purchase #5	$123.55	10.692%	$136.76	$136.76	$136.75	$136.80
Purchase #6	$158.57	9.131%	$173.049	$173.05	$173.05	$173.00
Purchase #7	$137.66	10.547%	$152.179	$152.18	$152.20	$152.20
7 purchase totals =	$864.80		$954.4664	$954.47	$954.45	$954.40