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	$189.73	3.843%	$197.0213	$197.02	$197.00	$197.00
Purchase #2	$235.46	13.702%	$267.7227	$267.72	$267.70	$267.70
Purchase #3	$129.87	4.774%	$136.07	$136.07	$136.05	$136.10
Purchase #4	$108.86	8.654%	$118.2807	$118.28	$118.30	$118.30
Purchase #5	$95.91	8.269%	$103.8408	$103.84	$103.85	$103.80
Purchase #6	$162.88	5.857%	$172.4199	$172.42	$172.40	$172.40
Purchase #7	$80.63	12.429%	$90.6515	$90.65	$90.65	$90.70
7 purchase totals =	$1,003.34		$1,086.0069	$1,086.00	$1,085.95	$1,086.00