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	$204.96	7.218%	$219.754	$219.75	$219.75	$219.80
Purchase #2	$33.50	11.203%	$37.253	$37.25	$37.25	$37.30
Purchase #3	$44.58	13.515%	$50.605	$50.61	$50.60	$50.60
Purchase #4	$71.87	8.861%	$78.2384	$78.24	$78.25	$78.20
Purchase #5	$64.55	10.232%	$71.1548	$71.15	$71.15	$71.20
Purchase #6	$136.66	8.227%	$147.903	$147.90	$147.90	$147.90
Purchase #7	$142.37	7.142%	$152.5381	$152.54	$152.55	$152.50
7 purchase totals =	$698.49		$757.4463	$757.44	$757.45	$757.50