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	$37.38	10.360%	$41.2526	$41.25	$41.25	$41.30
Purchase #2	$112.68	9.644%	$123.5469	$123.55	$123.55	$123.50
Purchase #3	$58.52	9.513%	$64.087	$64.09	$64.10	$64.10
Purchase #4	$201.38	10.597%	$222.7202	$222.72	$222.70	$222.70
Purchase #5	$35.51	13.696%	$40.3734	$40.37	$40.35	$40.40
Purchase #6	$216.61	9.108%	$236.3388	$236.34	$236.35	$236.30
Purchase #7	$55.29	3.281%	$57.1041	$57.10	$57.10	$57.10
7 purchase totals =	$717.37		$785.4230	$785.42	$785.40	$785.40