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	$31.89	6.276%	$33.8914	$33.89	$33.90	$33.90
Purchase #2	$31.48	9.423%	$34.4464	$34.45	$34.45	$34.40
Purchase #3	$42.27	9.605%	$46.33	$46.33	$46.35	$46.30
Purchase #4	$38.62	12.625%	$43.4958	$43.50	$43.50	$43.50
Purchase #5	$241.58	3.511%	$250.0619	$250.06	$250.05	$250.10
Purchase #6	$34.91	3.234%	$36.039	$36.04	$36.05	$36.00
Purchase #7	$229.90	9.411%	$251.5359	$251.54	$251.55	$251.50
7 purchase totals =	$650.65		$695.8004	$695.81	$695.85	$695.70