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	$129.72	8.874%	$141.2314	$141.23	$141.25	$141.20
Purchase #2	$159.30	5.196%	$167.5772	$167.58	$167.60	$167.60
Purchase #3	$84.27	7.141%	$90.2877	$90.29	$90.30	$90.30
Purchase #4	$247.79	5.803%	$262.1693	$262.17	$262.15	$262.20
Purchase #5	$155.66	12.363%	$174.9042	$174.90	$174.90	$174.90
Purchase #6	$85.90	11.120%	$95.4521	$95.45	$95.45	$95.50
Purchase #7	$183.67	13.807%	$209.0293	$209.03	$209.05	$209.00
7 purchase totals =	$1,046.31		$1,140.6512	$1,140.65	$1,140.70	$1,140.70