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	$33.81	13.450%	$38.3574	$38.36	$38.35	$38.40
Purchase #2	$71.78	9.368%	$78.5044	$78.50	$78.50	$78.50
Purchase #3	$139.51	8.165%	$150.901	$150.90	$150.90	$150.90
Purchase #4	$162.68	5.421%	$171.4989	$171.50	$171.50	$171.50
Purchase #5	$92.50	3.284%	$95.5377	$95.54	$95.55	$95.50
Purchase #6	$209.60	11.767%	$234.2636	$234.26	$234.25	$234.30
Purchase #7	$61.38	6.676%	$65.4777	$65.48	$65.50	$65.50
7 purchase totals =	$771.26		$834.5407	$834.54	$834.55	$834.60