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	$94.52	12.273%	$106.1204	$106.12	$106.10	$106.10
Purchase #2	$176.38	8.601%	$191.5504	$191.55	$191.55	$191.60
Purchase #3	$101.41	4.340%	$105.8112	$105.81	$105.80	$105.80
Purchase #4	$103.28	6.251%	$109.736	$109.74	$109.75	$109.70
Purchase #5	$32.38	8.540%	$35.1453	$35.15	$35.15	$35.10
Purchase #6	$142.31	12.797%	$160.5214	$160.52	$160.50	$160.50
Purchase #7	$244.89	7.249%	$262.6421	$262.64	$262.65	$262.60
7 purchase totals =	$895.17		$971.5268	$971.53	$971.50	$971.40