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	$243.43	13.225%	$275.6236	$275.62	$275.60	$275.60
Purchase #2	$69.26	12.851%	$78.1606	$78.16	$78.15	$78.20
Purchase #3	$47.38	12.438%	$53.2731	$53.27	$53.25	$53.30
Purchase #4	$186.40	6.584%	$198.6726	$198.67	$198.65	$198.70
Purchase #5	$236.87	3.761%	$245.7787	$245.78	$245.80	$245.80
Purchase #6	$250.90	5.699%	$265.1988	$265.20	$265.20	$265.20
Purchase #7	$61.25	6.781%	$65.4034	$65.40	$65.40	$65.40
7 purchase totals =	$1,095.49		$1,182.1108	$1,182.10	$1,182.05	$1,182.20