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	$125.42	9.690%	$137.5732	$137.57	$137.55	$137.60
Purchase #2	$137.91	13.699%	$156.8023	$156.80	$156.80	$156.80
Purchase #3	$191.43	11.189%	$212.8491	$212.85	$212.85	$212.80
Purchase #4	$58.66	6.645%	$62.558	$62.56	$62.55	$62.60
Purchase #5	$182.38	4.519%	$190.6218	$190.62	$190.60	$190.60
Purchase #6	$132.44	8.365%	$143.5186	$143.52	$143.50	$143.50
Purchase #7	$173.58	10.457%	$191.7313	$191.73	$191.75	$191.70
7 purchase totals =	$1,001.82		$1,095.6543	$1,095.65	$1,095.60	$1,095.60