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	$164.79	13.665%	$187.3086	$187.31	$187.30	$187.30
Purchase #2	$200.33	6.585%	$213.5217	$213.52	$213.50	$213.50
Purchase #3	$100.42	4.584%	$105.0233	$105.02	$105.00	$105.00
Purchase #4	$124.66	6.684%	$132.9923	$132.99	$133.00	$133.00
Purchase #5	$155.48	11.121%	$172.7709	$172.77	$172.75	$172.80
Purchase #6	$36.85	4.450%	$38.4898	$38.49	$38.50	$38.50
Purchase #7	$94.49	9.624%	$103.5837	$103.58	$103.60	$103.60
7 purchase totals =	$877.02		$953.6903	$953.68	$953.65	$953.70