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	$40.34	13.380%	$45.7375	$45.74	$45.75	$45.70
Purchase #2	$172.96	4.214%	$180.2485	$180.25	$180.25	$180.20
Purchase #3	$37.83	9.199%	$41.31	$41.31	$41.30	$41.30
Purchase #4	$39.81	9.758%	$43.6947	$43.69	$43.70	$43.70
Purchase #5	$211.65	5.839%	$224.0082	$224.01	$224.00	$224.00
Purchase #6	$93.57	11.644%	$104.4653	$104.47	$104.45	$104.50
Purchase #7	$69.40	12.167%	$77.8439	$77.84	$77.85	$77.80
7 purchase totals =	$665.56		$717.3081	$717.31	$717.30	$717.20