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	$82.94	3.161%	$85.5617	$85.56	$85.55	$85.60
Purchase #2	$118.76	4.727%	$124.3738	$124.37	$124.35	$124.40
Purchase #3	$35.77	3.785%	$37.1239	$37.12	$37.10	$37.10
Purchase #4	$108.95	13.227%	$123.3608	$123.36	$123.35	$123.40
Purchase #5	$224.46	12.423%	$252.3447	$252.34	$252.35	$252.30
Purchase #6	$132.65	6.605%	$141.4115	$141.41	$141.40	$141.40
Purchase #7	$142.63	11.660%	$159.2607	$159.26	$159.25	$159.30
7 purchase totals =	$846.16		$923.4371	$923.42	$923.35	$923.50