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	$169.61	13.136%	$191.89	$191.89	$191.90	$191.90
Purchase #2	$67.62	9.772%	$74.2278	$74.23	$74.25	$74.20
Purchase #3	$94.78	9.691%	$103.9651	$103.97	$103.95	$104.00
Purchase #4	$18.35	12.239%	$20.5959	$20.60	$20.60	$20.60
Purchase #5	$90.96	10.529%	$100.5372	$100.54	$100.55	$100.50
Purchase #6	$181.67	10.202%	$200.204	$200.20	$200.20	$200.20
Purchase #7	$170.90	9.817%	$187.6773	$187.68	$187.70	$187.70
7 purchase totals =	$793.89		$879.0973	$879.11	$879.15	$879.10