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	$58.82	5.150%	$61.8492	$61.85	$61.85	$61.80
Purchase #2	$73.53	11.121%	$81.7073	$81.71	$81.70	$81.70
Purchase #3	$131.99	5.663%	$139.4646	$139.46	$139.45	$139.50
Purchase #4	$99.53	12.241%	$111.7135	$111.71	$111.70	$111.70
Purchase #5	$199.87	5.660%	$211.1826	$211.18	$211.20	$211.20
Purchase #6	$148.31	9.793%	$162.834	$162.83	$162.85	$162.80
Purchase #7	$201.85	5.795%	$213.5472	$213.55	$213.55	$213.50
7 purchase totals =	$913.90		$982.2984	$982.29	$982.30	$982.20