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	$64.74	12.167%	$72.6169	$72.62	$72.60	$72.60
Purchase #2	$44.26	7.717%	$47.6755	$47.68	$47.70	$47.70
Purchase #3	$181.39	9.620%	$198.8397	$198.84	$198.85	$198.80
Purchase #4	$49.32	11.142%	$54.8152	$54.82	$54.80	$54.80
Purchase #5	$197.79	12.698%	$222.9054	$222.91	$222.90	$222.90
Purchase #6	$217.98	12.548%	$245.3321	$245.33	$245.35	$245.30
Purchase #7	$182.98	4.845%	$191.8454	$191.85	$191.85	$191.80
7 purchase totals =	$938.46		$1,034.0302	$1,034.05	$1,034.05	$1,033.90