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	$137.76	12.736%	$155.3051	$155.31	$155.30	$155.30
Purchase #2	$133.80	12.370%	$150.3511	$150.35	$150.35	$150.40
Purchase #3	$63.39	13.418%	$71.8957	$71.90	$71.90	$71.90
Purchase #4	$151.37	5.359%	$159.4819	$159.48	$159.50	$159.50
Purchase #5	$138.87	7.776%	$149.6685	$149.67	$149.65	$149.70
Purchase #6	$189.51	10.661%	$209.7137	$209.71	$209.70	$209.70
Purchase #7	$148.27	9.664%	$162.5988	$162.60	$162.60	$162.60
7 purchase totals =	$962.97		$1,059.0148	$1,059.02	$1,059.00	$1,059.10