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	$103.25	10.244%	$113.8269	$113.83	$113.85	$113.80
Purchase #2	$195.72	13.201%	$221.557	$221.56	$221.55	$221.60
Purchase #3	$38.46	10.340%	$42.4368	$42.44	$42.45	$42.40
Purchase #4	$177.31	7.546%	$190.6898	$190.69	$190.70	$190.70
Purchase #5	$151.79	12.253%	$170.3888	$170.39	$170.40	$170.40
Purchase #6	$76.35	11.745%	$85.3173	$85.32	$85.30	$85.30
Purchase #7	$10.25	3.696%	$10.6288	$10.63	$10.65	$10.60
7 purchase totals =	$753.13		$834.8454	$834.86	$834.90	$834.80