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	$80.86	3.485%	$83.678	$83.68	$83.70	$83.70
Purchase #2	$162.26	12.225%	$182.0963	$182.10	$182.10	$182.10
Purchase #3	$61.75	7.644%	$66.4702	$66.47	$66.45	$66.50
Purchase #4	$240.72	13.414%	$273.0102	$273.01	$273.00	$273.00
Purchase #5	$221.49	13.230%	$250.7931	$250.79	$250.80	$250.80
Purchase #6	$52.89	12.624%	$59.5668	$59.57	$59.55	$59.60
Purchase #7	$181.92	4.643%	$190.3665	$190.37	$190.35	$190.40
7 purchase totals =	$1,001.89		$1,105.9811	$1,105.99	$1,105.95	$1,106.10