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	$167.39	13.276%	$189.6127	$189.61	$189.60	$189.60
Purchase #2	$152.44	9.438%	$166.8273	$166.83	$166.85	$166.80
Purchase #3	$196.66	4.558%	$205.6238	$205.62	$205.60	$205.60
Purchase #4	$149.52	4.755%	$156.6297	$156.63	$156.65	$156.60
Purchase #5	$149.57	10.427%	$165.1657	$165.17	$165.15	$165.20
Purchase #6	$138.37	12.320%	$155.4172	$155.42	$155.40	$155.40
Purchase #7	$123.48	4.815%	$129.4256	$129.43	$129.45	$129.40
7 purchase totals =	$1,077.43		$1,168.7020	$1,168.71	$1,168.70	$1,168.60