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	$178.66	5.325%	$188.1736	$188.17	$188.15	$188.20
Purchase #2	$113.35	11.529%	$126.4181	$126.42	$126.40	$126.40
Purchase #3	$40.27	12.624%	$45.3537	$45.35	$45.35	$45.40
Purchase #4	$222.71	9.348%	$243.5289	$243.53	$243.55	$243.50
Purchase #5	$191.61	11.197%	$213.0646	$213.06	$213.05	$213.10
Purchase #6	$192.61	3.511%	$199.3725	$199.37	$199.35	$199.40
Purchase #7	$128.34	9.455%	$140.4745	$140.47	$140.45	$140.50
7 purchase totals =	$1,067.55		$1,156.3859	$1,156.37	$1,156.30	$1,156.50