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	$130.31	7.342%	$139.8774	$139.88	$139.90	$139.90
Purchase #2	$165.56	11.544%	$184.6722	$184.67	$184.65	$184.70
Purchase #3	$170.42	13.533%	$193.4829	$193.48	$193.50	$193.50
Purchase #4	$130.29	10.819%	$144.3861	$144.39	$144.40	$144.40
Purchase #5	$93.37	11.797%	$104.3849	$104.38	$104.40	$104.40
Purchase #6	$96.64	4.872%	$101.3483	$101.35	$101.35	$101.30
Purchase #7	$185.45	5.287%	$195.2547	$195.25	$195.25	$195.30
7 purchase totals =	$972.04		$1,063.4065	$1,063.40	$1,063.45	$1,063.50