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	$65.38	8.456%	$70.9085	$70.91	$70.90	$70.90
Purchase #2	$80.91	11.507%	$90.2203	$90.22	$90.20	$90.20
Purchase #3	$226.69	7.824%	$244.4262	$244.43	$244.45	$244.40
Purchase #4	$49.66	5.312%	$52.2979	$52.30	$52.30	$52.30
Purchase #5	$93.64	7.614%	$100.7697	$100.77	$100.75	$100.80
Purchase #6	$243.44	11.574%	$271.6157	$271.62	$271.60	$271.60
Purchase #7	$190.31	13.710%	$216.4015	$216.40	$216.40	$216.40
7 purchase totals =	$950.03		$1,046.6398	$1,046.65	$1,046.60	$1,046.60