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	$148.39	11.483%	$165.4296	$165.43	$165.45	$165.40
Purchase #2	$195.64	10.466%	$216.1157	$216.12	$216.10	$216.10
Purchase #3	$102.51	4.142%	$106.756	$106.76	$106.75	$106.80
Purchase #4	$44.40	13.435%	$50.3651	$50.37	$50.35	$50.40
Purchase #5	$243.78	6.484%	$259.5867	$259.59	$259.60	$259.60
Purchase #6	$36.40	6.131%	$38.6317	$38.63	$38.65	$38.60
Purchase #7	$9.90	5.577%	$10.4521	$10.45	$10.45	$10.50
7 purchase totals =	$781.02		$847.3369	$847.35	$847.35	$847.40