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	$113.81	3.548%	$117.848	$117.85	$117.85	$117.80
Purchase #2	$81.43	4.747%	$85.2955	$85.30	$85.30	$85.30
Purchase #3	$172.65	6.197%	$183.3491	$183.35	$183.35	$183.30
Purchase #4	$37.84	10.694%	$41.8866	$41.89	$41.90	$41.90
Purchase #5	$234.84	8.794%	$255.4918	$255.49	$255.50	$255.50
Purchase #6	$35.50	5.797%	$37.5579	$37.56	$37.55	$37.60
Purchase #7	$135.81	3.497%	$140.5593	$140.56	$140.55	$140.60
7 purchase totals =	$811.88		$861.9882	$862.00	$862.00	$862.00