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	$152.54	10.603%	$168.7138	$168.71	$168.70	$168.70
Purchase #2	$71.61	9.619%	$78.4982	$78.50	$78.50	$78.50
Purchase #3	$143.74	11.608%	$160.4253	$160.43	$160.45	$160.40
Purchase #4	$125.98	5.342%	$132.7099	$132.71	$132.70	$132.70
Purchase #5	$82.66	12.158%	$92.7098	$92.71	$92.70	$92.70
Purchase #6	$82.45	13.356%	$93.462	$93.46	$93.45	$93.50
Purchase #7	$6.43	9.469%	$7.0389	$7.04	$7.05	$7.00
7 purchase totals =	$665.41		$733.5579	$733.56	$733.55	$733.50