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	$60.81	3.487%	$62.9304	$62.93	$62.95	$62.90
Purchase #2	$52.86	3.801%	$54.8692	$54.87	$54.85	$54.90
Purchase #3	$181.95	9.648%	$199.5045	$199.50	$199.50	$199.50
Purchase #4	$32.41	9.788%	$35.5823	$35.58	$35.60	$35.60
Purchase #5	$116.46	12.681%	$131.2283	$131.23	$131.25	$131.20
Purchase #6	$18.88	12.536%	$21.2468	$21.25	$21.25	$21.20
Purchase #7	$167.48	5.850%	$177.2776	$177.28	$177.30	$177.30
7 purchase totals =	$630.85		$682.6391	$682.64	$682.70	$682.60