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	$144.66	6.853%	$154.5735	$154.57	$154.55	$154.60
Purchase #2	$28.42	6.437%	$30.2494	$30.25	$30.25	$30.20
Purchase #3	$186.48	4.622%	$195.0991	$195.10	$195.10	$195.10
Purchase #4	$35.77	4.675%	$37.4422	$37.44	$37.45	$37.40
Purchase #5	$116.39	9.669%	$127.6437	$127.64	$127.65	$127.60
Purchase #6	$160.98	11.513%	$179.5136	$179.51	$179.50	$179.50
Purchase #7	$67.71	6.785%	$72.3041	$72.30	$72.30	$72.30
7 purchase totals =	$740.41		$796.8256	$796.81	$796.80	$796.70