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	$110.73	10.557%	$122.4198	$122.42	$122.40	$122.40
Purchase #2	$56.64	8.345%	$61.3666	$61.37	$61.35	$61.40
Purchase #3	$38.34	11.868%	$42.8902	$42.89	$42.90	$42.90
Purchase #4	$70.51	13.678%	$80.1544	$80.15	$80.15	$80.20
Purchase #5	$235.66	10.858%	$261.248	$261.25	$261.25	$261.20
Purchase #6	$100.50	10.593%	$111.146	$111.15	$111.15	$111.10
Purchase #7	$66.68	8.326%	$72.2318	$72.23	$72.25	$72.20
7 purchase totals =	$679.06		$751.4568	$751.46	$751.45	$751.40