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	$104.51	8.211%	$113.0913	$113.09	$113.10	$113.10
Purchase #2	$26.80	13.185%	$30.3336	$30.33	$30.35	$30.30
Purchase #3	$127.59	10.197%	$140.6004	$140.60	$140.60	$140.60
Purchase #4	$105.46	5.826%	$111.6041	$111.60	$111.60	$111.60
Purchase #5	$97.72	3.317%	$100.9614	$100.96	$100.95	$101.00
Purchase #6	$36.57	3.660%	$37.9085	$37.91	$37.90	$37.90
Purchase #7	$192.97	6.764%	$206.0225	$206.02	$206.00	$206.00
7 purchase totals =	$691.62		$740.5218	$740.51	$740.50	$740.50