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	$117.69	13.549%	$133.6358	$133.64	$133.65	$133.60
Purchase #2	$26.35	9.494%	$28.8517	$28.85	$28.85	$28.90
Purchase #3	$39.75	7.578%	$42.7623	$42.76	$42.75	$42.80
Purchase #4	$137.72	9.561%	$150.8874	$150.89	$150.90	$150.90
Purchase #5	$211.71	4.274%	$220.7585	$220.76	$220.75	$220.80
Purchase #6	$231.25	8.318%	$250.4854	$250.49	$250.50	$250.50
Purchase #7	$244.76	5.597%	$258.4592	$258.46	$258.45	$258.50
7 purchase totals =	$1,009.23		$1,085.8403	$1,085.85	$1,085.85	$1,086.00