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	$36.79	12.541%	$41.4038	$41.40	$41.40	$41.40
Purchase #2	$205.50	6.646%	$219.1575	$219.16	$219.15	$219.20
Purchase #3	$35.88	11.273%	$39.9248	$39.92	$39.90	$39.90
Purchase #4	$109.59	3.281%	$113.1856	$113.19	$113.20	$113.20
Purchase #5	$107.46	3.405%	$111.119	$111.12	$111.10	$111.10
Purchase #6	$87.94	4.106%	$91.5508	$91.55	$91.55	$91.60
Purchase #7	$247.30	11.368%	$275.4131	$275.41	$275.40	$275.40
7 purchase totals =	$830.46		$891.7546	$891.75	$891.70	$891.80