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	$215.77	4.495%	$225.4689	$225.47	$225.45	$225.50
Purchase #2	$201.45	8.662%	$218.8996	$218.90	$218.90	$218.90
Purchase #3	$167.39	10.185%	$184.4387	$184.44	$184.45	$184.40
Purchase #4	$140.64	13.439%	$159.5406	$159.54	$159.55	$159.50
Purchase #5	$51.56	7.265%	$55.3058	$55.31	$55.30	$55.30
Purchase #6	$175.53	10.608%	$194.1502	$194.15	$194.15	$194.20
Purchase #7	$222.98	9.660%	$244.5199	$244.52	$244.50	$244.50
7 purchase totals =	$1,175.32		$1,282.3237	$1,282.33	$1,282.30	$1,282.30