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	$115.49	7.243%	$123.8549	$123.85	$123.85	$123.90
Purchase #2	$197.53	5.824%	$209.0341	$209.03	$209.05	$209.00
Purchase #3	$7.32	5.213%	$7.7016	$7.70	$7.70	$7.70
Purchase #4	$239.55	5.697%	$253.1972	$253.20	$253.20	$253.20
Purchase #5	$72.55	11.189%	$80.6676	$80.67	$80.65	$80.70
Purchase #6	$180.40	6.321%	$191.8031	$191.80	$191.80	$191.80
Purchase #7	$127.79	7.675%	$137.5979	$137.60	$137.60	$137.60
7 purchase totals =	$940.63		$1,003.8564	$1,003.85	$1,003.85	$1,003.90