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	$182.79	11.804%	$204.3665	$204.37	$204.35	$204.40
Purchase #2	$44.59	11.240%	$49.6019	$49.60	$49.60	$49.60
Purchase #3	$131.85	7.616%	$141.8917	$141.89	$141.90	$141.90
Purchase #4	$250.52	9.299%	$273.8159	$273.82	$273.80	$273.80
Purchase #5	$122.34	7.496%	$131.5106	$131.51	$131.50	$131.50
Purchase #6	$222.60	13.693%	$253.0806	$253.08	$253.10	$253.10
Purchase #7	$236.47	4.419%	$246.9196	$246.92	$246.90	$246.90
7 purchase totals =	$1,191.16		$1,301.1868	$1,301.19	$1,301.15	$1,301.20