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	$223.41	4.432%	$233.3115	$233.31	$233.30	$233.30
Purchase #2	$61.77	10.675%	$68.3639	$68.36	$68.35	$68.40
Purchase #3	$45.79	5.340%	$48.2352	$48.24	$48.25	$48.20
Purchase #4	$90.46	3.459%	$93.589	$93.59	$93.60	$93.60
Purchase #5	$200.94	8.183%	$217.3829	$217.38	$217.40	$217.40
Purchase #6	$143.63	8.358%	$155.6346	$155.63	$155.65	$155.60
Purchase #7	$236.82	11.849%	$264.8808	$264.88	$264.90	$264.90
7 purchase totals =	$1,002.82		$1,081.3979	$1,081.39	$1,081.45	$1,081.40