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	$195.62	6.649%	$208.6268	$208.63	$208.65	$208.60
Purchase #2	$125.55	11.342%	$139.7899	$139.79	$139.80	$139.80
Purchase #3	$145.67	8.668%	$158.2967	$158.30	$158.30	$158.30
Purchase #4	$40.59	11.332%	$45.1897	$45.19	$45.20	$45.20
Purchase #5	$210.63	11.260%	$234.3469	$234.35	$234.35	$234.30
Purchase #6	$192.36	3.590%	$199.2657	$199.27	$199.25	$199.30
Purchase #7	$93.31	7.562%	$100.3661	$100.37	$100.35	$100.40
7 purchase totals =	$1,003.73		$1,085.8818	$1,085.90	$1,085.90	$1,085.90