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	$136.97	10.686%	$151.6066	$151.61	$151.60	$151.60
Purchase #2	$158.63	5.570%	$167.4657	$167.47	$167.45	$167.50
Purchase #3	$179.98	5.295%	$189.5099	$189.51	$189.50	$189.50
Purchase #4	$29.42	11.753%	$32.8777	$32.88	$32.90	$32.90
Purchase #5	$189.61	12.717%	$213.7227	$213.72	$213.70	$213.70
Purchase #6	$239.31	13.633%	$271.9351	$271.94	$271.95	$271.90
Purchase #7	$160.79	11.260%	$178.895	$178.90	$178.90	$178.90
7 purchase totals =	$1,094.71		$1,206.0127	$1,206.03	$1,206.00	$1,206.00