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	$101.91	10.202%	$112.3069	$112.31	$112.30	$112.30
Purchase #2	$29.64	9.374%	$32.4185	$32.42	$32.40	$32.40
Purchase #3	$112.77	12.371%	$126.7208	$126.72	$126.70	$126.70
Purchase #4	$63.73	12.410%	$71.6389	$71.64	$71.65	$71.60
Purchase #5	$131.56	11.525%	$146.7223	$146.72	$146.70	$146.70
Purchase #6	$55.31	12.434%	$62.1872	$62.19	$62.20	$62.20
Purchase #7	$126.33	13.221%	$143.0321	$143.03	$143.05	$143.00
7 purchase totals =	$621.25		$695.0267	$695.03	$695.00	$694.90