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	$195.78	13.631%	$222.4668	$222.47	$222.45	$222.50
Purchase #2	$59.84	13.287%	$67.7909	$67.79	$67.80	$67.80
Purchase #3	$50.65	5.276%	$53.3223	$53.32	$53.30	$53.30
Purchase #4	$67.62	5.412%	$71.2796	$71.28	$71.30	$71.30
Purchase #5	$132.71	6.547%	$141.3985	$141.40	$141.40	$141.40
Purchase #6	$225.54	12.584%	$253.922	$253.92	$253.90	$253.90
Purchase #7	$46.34	8.473%	$50.2664	$50.27	$50.25	$50.30
7 purchase totals =	$778.48		$860.4465	$860.45	$860.40	$860.50