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	$151.31	6.186%	$160.67	$160.67	$160.65	$160.70
Purchase #2	$85.46	6.444%	$90.967	$90.97	$90.95	$91.00
Purchase #3	$55.54	11.545%	$61.9521	$61.95	$61.95	$62.00
Purchase #4	$248.60	10.705%	$275.2126	$275.21	$275.20	$275.20
Purchase #5	$100.54	4.477%	$105.0412	$105.04	$105.05	$105.00
Purchase #6	$133.44	5.800%	$141.1795	$141.18	$141.20	$141.20
Purchase #7	$199.74	10.830%	$221.3718	$221.37	$221.35	$221.40
7 purchase totals =	$974.63		$1,056.3942	$1,056.39	$1,056.35	$1,056.50