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	$147.36	10.498%	$162.8299	$162.83	$162.85	$162.80
Purchase #2	$149.64	13.518%	$169.8683	$169.87	$169.85	$169.90
Purchase #3	$29.91	11.168%	$33.2503	$33.25	$33.25	$33.30
Purchase #4	$55.73	6.504%	$59.3547	$59.35	$59.35	$59.40
Purchase #5	$185.25	8.576%	$201.137	$201.14	$201.15	$201.10
Purchase #6	$130.27	12.527%	$146.5889	$146.59	$146.60	$146.60
Purchase #7	$140.91	12.336%	$158.2927	$158.29	$158.30	$158.30
7 purchase totals =	$839.07		$931.3218	$931.32	$931.35	$931.40