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	$130.86	10.639%	$144.7822	$144.78	$144.80	$144.80
Purchase #2	$71.31	9.759%	$78.2691	$78.27	$78.25	$78.30
Purchase #3	$60.66	3.410%	$62.7285	$62.73	$62.75	$62.70
Purchase #4	$23.51	11.428%	$26.1967	$26.20	$26.20	$26.20
Purchase #5	$47.89	13.442%	$54.3274	$54.33	$54.35	$54.30
Purchase #6	$74.51	12.193%	$83.595	$83.60	$83.60	$83.60
Purchase #7	$245.66	13.361%	$278.4826	$278.48	$278.50	$278.50
7 purchase totals =	$654.40		$728.3815	$728.39	$728.45	$728.40