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	$193.52	7.606%	$208.2391	$208.24	$208.25	$208.20
Purchase #2	$82.28	4.332%	$85.8444	$85.84	$85.85	$85.80
Purchase #3	$243.82	10.667%	$269.8283	$269.83	$269.85	$269.80
Purchase #4	$223.32	6.336%	$237.4696	$237.47	$237.45	$237.50
Purchase #5	$63.84	13.797%	$72.648	$72.65	$72.65	$72.60
Purchase #6	$246.36	11.676%	$275.125	$275.13	$275.15	$275.10
Purchase #7	$211.43	7.669%	$227.6446	$227.64	$227.65	$227.60
7 purchase totals =	$1,264.57		$1,376.7990	$1,376.80	$1,376.85	$1,376.60