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	$198.63	5.149%	$208.8575	$208.86	$208.85	$208.90
Purchase #2	$73.54	3.776%	$76.3169	$76.32	$76.30	$76.30
Purchase #3	$39.27	7.408%	$42.1791	$42.18	$42.20	$42.20
Purchase #4	$33.37	7.307%	$35.8083	$35.81	$35.80	$35.80
Purchase #5	$30.75	7.830%	$33.1577	$33.16	$33.15	$33.20
Purchase #6	$214.74	7.319%	$230.4568	$230.46	$230.45	$230.50
Purchase #7	$126.95	10.108%	$139.7821	$139.78	$139.80	$139.80
7 purchase totals =	$717.25		$766.5584	$766.57	$766.55	$766.70