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	$227.48	6.116%	$241.3927	$241.39	$241.40	$241.40
Purchase #2	$229.79	7.783%	$247.6746	$247.67	$247.65	$247.70
Purchase #3	$119.45	6.699%	$127.452	$127.45	$127.45	$127.50
Purchase #4	$60.74	13.830%	$69.1403	$69.14	$69.15	$69.10
Purchase #5	$41.55	9.233%	$45.3863	$45.39	$45.40	$45.40
Purchase #6	$245.45	4.349%	$256.1246	$256.12	$256.10	$256.10
Purchase #7	$79.72	4.573%	$83.3656	$83.37	$83.35	$83.40
7 purchase totals =	$1,004.18		$1,070.5361	$1,070.53	$1,070.50	$1,070.60