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	$164.92	13.284%	$186.828	$186.83	$186.85	$186.80
Purchase #2	$106.90	9.769%	$117.3431	$117.34	$117.35	$117.30
Purchase #3	$151.50	6.852%	$161.8808	$161.88	$161.90	$161.90
Purchase #4	$160.70	7.146%	$172.1836	$172.18	$172.20	$172.20
Purchase #5	$170.70	5.143%	$179.4791	$179.48	$179.50	$179.50
Purchase #6	$93.50	11.549%	$104.2983	$104.30	$104.30	$104.30
Purchase #7	$168.78	3.409%	$174.5337	$174.53	$174.55	$174.50
7 purchase totals =	$1,017.00		$1,096.5466	$1,096.54	$1,096.65	$1,096.50