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	$174.65	7.797%	$188.2675	$188.27	$188.25	$188.30
Purchase #2	$90.84	11.603%	$101.3802	$101.38	$101.40	$101.40
Purchase #3	$180.78	12.544%	$203.457	$203.46	$203.45	$203.50
Purchase #4	$37.75	12.733%	$42.5567	$42.56	$42.55	$42.60
Purchase #5	$193.36	12.748%	$218.0095	$218.01	$218.00	$218.00
Purchase #6	$208.33	9.146%	$227.3839	$227.38	$227.40	$227.40
Purchase #7	$165.50	12.584%	$186.3265	$186.33	$186.35	$186.30
7 purchase totals =	$1,051.21		$1,167.3813	$1,167.39	$1,167.40	$1,167.50