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	$173.86	4.753%	$182.1236	$182.12	$182.10	$182.10
Purchase #2	$129.99	7.314%	$139.4975	$139.50	$139.50	$139.50
Purchase #3	$112.90	5.804%	$119.4527	$119.45	$119.45	$119.50
Purchase #4	$170.83	11.684%	$190.7898	$190.79	$190.80	$190.80
Purchase #5	$56.41	5.387%	$59.4488	$59.45	$59.45	$59.40
Purchase #6	$250.29	11.768%	$279.7441	$279.74	$279.75	$279.70
Purchase #7	$61.87	10.682%	$68.479	$68.48	$68.50	$68.50
7 purchase totals =	$956.15		$1,039.5355	$1,039.53	$1,039.55	$1,039.50