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	$227.36	5.687%	$240.29	$240.29	$240.30	$240.30
Purchase #2	$43.35	11.448%	$48.3127	$48.31	$48.30	$48.30
Purchase #3	$126.47	3.233%	$130.5588	$130.56	$130.55	$130.60
Purchase #4	$70.45	11.769%	$78.7413	$78.74	$78.75	$78.70
Purchase #5	$133.61	4.334%	$139.4007	$139.40	$139.40	$139.40
Purchase #6	$132.59	7.749%	$142.8644	$142.86	$142.85	$142.90
Purchase #7	$28.98	8.655%	$31.4882	$31.49	$31.50	$31.50
7 purchase totals =	$762.81		$811.6561	$811.65	$811.65	$811.70