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	$179.85	11.504%	$200.5399	$200.54	$200.55	$200.50
Purchase #2	$207.99	11.504%	$231.9172	$231.92	$231.90	$231.90
Purchase #3	$38.61	13.430%	$43.7953	$43.80	$43.80	$43.80
Purchase #4	$18.31	13.457%	$20.774	$20.77	$20.75	$20.80
Purchase #5	$82.92	3.523%	$85.8413	$85.84	$85.85	$85.80
Purchase #6	$175.51	7.698%	$189.0208	$189.02	$189.00	$189.00
Purchase #7	$179.36	3.176%	$185.0565	$185.06	$185.05	$185.10
7 purchase totals =	$882.55		$956.9450	$956.95	$956.90	$956.90