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	$109.54	12.873%	$123.6411	$123.64	$123.65	$123.60
Purchase #2	$66.40	13.743%	$75.5254	$75.53	$75.55	$75.50
Purchase #3	$122.51	12.486%	$137.8066	$137.81	$137.80	$137.80
Purchase #4	$190.36	12.384%	$213.9342	$213.93	$213.95	$213.90
Purchase #5	$195.27	11.721%	$218.1576	$218.16	$218.15	$218.20
Purchase #6	$87.46	3.365%	$90.403	$90.40	$90.40	$90.40
Purchase #7	$249.72	13.212%	$282.713	$282.71	$282.70	$282.70
7 purchase totals =	$1,021.26		$1,142.1809	$1,142.18	$1,142.20	$1,142.10