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	$238.28	10.282%	$262.7799	$262.78	$262.80	$262.80
Purchase #2	$248.64	12.802%	$280.4709	$280.47	$280.45	$280.50
Purchase #3	$149.46	11.514%	$166.6688	$166.67	$166.65	$166.70
Purchase #4	$88.75	11.498%	$98.9545	$98.95	$98.95	$99.00
Purchase #5	$93.84	8.388%	$101.7113	$101.71	$101.70	$101.70
Purchase #6	$168.88	11.599%	$188.4684	$188.47	$188.45	$188.50
Purchase #7	$132.54	9.256%	$144.8079	$144.81	$144.80	$144.80
7 purchase totals =	$1,120.39		$1,243.8617	$1,243.86	$1,243.80	$1,244.00