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	$221.56	13.576%	$251.639	$251.64	$251.65	$251.60
Purchase #2	$76.71	9.287%	$83.8341	$83.83	$83.85	$83.80
Purchase #3	$237.90	10.758%	$263.4933	$263.49	$263.50	$263.50
Purchase #4	$98.31	10.511%	$108.6434	$108.64	$108.65	$108.60
Purchase #5	$6.58	11.349%	$7.3268	$7.33	$7.35	$7.30
Purchase #6	$85.95	11.174%	$95.5541	$95.55	$95.55	$95.60
Purchase #7	$208.32	13.316%	$236.0599	$236.06	$236.05	$236.10
7 purchase totals =	$935.33		$1,046.5506	$1,046.54	$1,046.60	$1,046.50