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	$36.33	3.354%	$37.5485	$37.55	$37.55	$37.50
Purchase #2	$123.96	6.645%	$132.1971	$132.20	$132.20	$132.20
Purchase #3	$174.43	13.189%	$197.4356	$197.44	$197.45	$197.40
Purchase #4	$63.25	13.718%	$71.9266	$71.93	$71.95	$71.90
Purchase #5	$17.76	11.600%	$19.8202	$19.82	$19.80	$19.80
Purchase #6	$78.26	5.369%	$82.4618	$82.46	$82.45	$82.50
Purchase #7	$61.73	8.595%	$67.0357	$67.04	$67.05	$67.00
7 purchase totals =	$555.72		$608.4255	$608.44	$608.45	$608.30