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	$198.86	9.180%	$217.1153	$217.12	$217.10	$217.10
Purchase #2	$227.34	3.333%	$234.9172	$234.92	$234.90	$234.90
Purchase #3	$17.92	13.577%	$20.353	$20.35	$20.35	$20.40
Purchase #4	$157.75	5.151%	$165.8757	$165.88	$165.90	$165.90
Purchase #5	$176.49	11.503%	$196.7916	$196.79	$196.80	$196.80
Purchase #6	$123.52	11.252%	$137.4185	$137.42	$137.40	$137.40
Purchase #7	$196.53	8.271%	$212.785	$212.79	$212.80	$212.80
7 purchase totals =	$1,098.41		$1,185.2563	$1,185.27	$1,185.25	$1,185.30