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	$68.61	5.274%	$72.2285	$72.23	$72.25	$72.20
Purchase #2	$149.72	8.627%	$162.6363	$162.64	$162.65	$162.60
Purchase #3	$236.66	8.428%	$256.6057	$256.61	$256.60	$256.60
Purchase #4	$195.27	5.350%	$205.7169	$205.72	$205.70	$205.70
Purchase #5	$76.73	10.380%	$84.6946	$84.69	$84.70	$84.70
Purchase #6	$206.53	4.202%	$215.2084	$215.21	$215.20	$215.20
Purchase #7	$39.65	6.714%	$42.3121	$42.31	$42.30	$42.30
7 purchase totals =	$973.17		$1,039.4025	$1,039.41	$1,039.40	$1,039.30