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	$231.64	10.673%	$256.3629	$256.36	$256.35	$256.40
Purchase #2	$85.44	5.223%	$89.9025	$89.90	$89.90	$89.90
Purchase #3	$26.27	10.716%	$29.0851	$29.09	$29.10	$29.10
Purchase #4	$218.60	6.351%	$232.4833	$232.48	$232.50	$232.50
Purchase #5	$6.26	13.270%	$7.0907	$7.09	$7.10	$7.10
Purchase #6	$165.32	4.557%	$172.8536	$172.85	$172.85	$172.90
Purchase #7	$242.62	5.355%	$255.6123	$255.61	$255.60	$255.60
7 purchase totals =	$976.15		$1,043.3904	$1,043.38	$1,043.40	$1,043.50