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	$60.29	8.830%	$65.6136	$65.61	$65.60	$65.60
Purchase #2	$31.91	11.594%	$35.6096	$35.61	$35.60	$35.60
Purchase #3	$29.80	6.424%	$31.7144	$31.71	$31.70	$31.70
Purchase #4	$90.44	9.853%	$99.3511	$99.35	$99.35	$99.40
Purchase #5	$32.61	9.214%	$35.6147	$35.61	$35.60	$35.60
Purchase #6	$204.56	7.690%	$220.2907	$220.29	$220.30	$220.30
Purchase #7	$61.70	9.681%	$67.6732	$67.67	$67.65	$67.70
7 purchase totals =	$511.31		$555.8673	$555.85	$555.80	$555.90