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	$153.73	7.400%	$165.106	$165.11	$165.10	$165.10
Purchase #2	$38.29	5.704%	$40.4741	$40.47	$40.45	$40.50
Purchase #3	$46.73	7.756%	$50.3544	$50.35	$50.35	$50.40
Purchase #4	$118.27	13.690%	$134.4612	$134.46	$134.45	$134.50
Purchase #5	$154.45	7.730%	$166.389	$166.39	$166.40	$166.40
Purchase #6	$156.66	7.204%	$167.9458	$167.95	$167.95	$167.90
Purchase #7	$194.69	9.522%	$213.2284	$213.23	$213.25	$213.20
7 purchase totals =	$862.82		$937.9589	$937.96	$937.95	$938.00