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	$156.57	3.674%	$162.3224	$162.32	$162.30	$162.30
Purchase #2	$237.35	11.795%	$265.3454	$265.35	$265.35	$265.30
Purchase #3	$183.32	3.312%	$189.3916	$189.39	$189.40	$189.40
Purchase #4	$199.31	11.866%	$222.9601	$222.96	$222.95	$223.00
Purchase #5	$87.76	13.683%	$99.7682	$99.77	$99.75	$99.80
Purchase #6	$131.55	4.470%	$137.4303	$137.43	$137.45	$137.40
Purchase #7	$136.31	5.828%	$144.2541	$144.25	$144.25	$144.30
7 purchase totals =	$1,132.17		$1,221.4721	$1,221.47	$1,221.45	$1,221.50