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	$93.43	11.129%	$103.8278	$103.83	$103.85	$103.80
Purchase #2	$180.26	4.599%	$188.5502	$188.55	$188.55	$188.60
Purchase #3	$126.83	9.774%	$139.2264	$139.23	$139.25	$139.20
Purchase #4	$11.56	10.198%	$12.7389	$12.74	$12.75	$12.70
Purchase #5	$213.26	4.273%	$222.3726	$222.37	$222.35	$222.40
Purchase #6	$247.26	6.322%	$262.8918	$262.89	$262.90	$262.90
Purchase #7	$30.57	4.247%	$31.8683	$31.87	$31.85	$31.90
7 purchase totals =	$903.17		$961.4760	$961.48	$961.50	$961.50