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	$128.74	9.312%	$140.7283	$140.73	$140.75	$140.70
Purchase #2	$175.84	11.600%	$196.2374	$196.24	$196.25	$196.20
Purchase #3	$218.46	9.442%	$239.087	$239.09	$239.10	$239.10
Purchase #4	$116.45	10.182%	$128.3069	$128.31	$128.30	$128.30
Purchase #5	$78.38	4.518%	$81.9212	$81.92	$81.90	$81.90
Purchase #6	$249.78	9.249%	$272.8822	$272.88	$272.90	$272.90
Purchase #7	$41.86	8.756%	$45.5253	$45.53	$45.55	$45.50
7 purchase totals =	$1,009.51		$1,104.6883	$1,104.70	$1,104.75	$1,104.60