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	$5.69	3.275%	$5.8763	$5.88	$5.90	$5.90
Purchase #2	$49.70	7.843%	$53.598	$53.60	$53.60	$53.60
Purchase #3	$33.65	8.563%	$36.5314	$36.53	$36.55	$36.50
Purchase #4	$37.43	12.266%	$42.0212	$42.02	$42.00	$42.00
Purchase #5	$50.40	10.252%	$55.567	$55.57	$55.55	$55.60
Purchase #6	$109.26	10.288%	$120.5007	$120.50	$120.50	$120.50
Purchase #7	$117.96	11.712%	$131.7755	$131.78	$131.80	$131.80
7 purchase totals =	$404.09		$445.8701	$445.88	$445.90	$445.90