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	$208.85	3.836%	$216.8615	$216.86	$216.85	$216.90
Purchase #2	$37.31	13.440%	$42.3245	$42.32	$42.30	$42.30
Purchase #3	$231.71	3.800%	$240.515	$240.52	$240.50	$240.50
Purchase #4	$11.89	7.533%	$12.7857	$12.79	$12.80	$12.80
Purchase #5	$237.81	10.315%	$262.3401	$262.34	$262.35	$262.30
Purchase #6	$105.33	9.352%	$115.1805	$115.18	$115.20	$115.20
Purchase #7	$29.63	8.407%	$32.121	$32.12	$32.10	$32.10
7 purchase totals =	$862.53		$922.1283	$922.13	$922.10	$922.10