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	$81.79	4.423%	$85.4076	$85.41	$85.40	$85.40
Purchase #2	$160.66	10.871%	$178.1253	$178.13	$178.15	$178.10
Purchase #3	$179.38	5.701%	$189.6065	$189.61	$189.60	$189.60
Purchase #4	$44.70	3.721%	$46.3633	$46.36	$46.35	$46.40
Purchase #5	$37.46	9.145%	$40.8857	$40.89	$40.90	$40.90
Purchase #6	$168.68	3.359%	$174.346	$174.35	$174.35	$174.30
Purchase #7	$228.90	8.584%	$248.5488	$248.55	$248.55	$248.50
7 purchase totals =	$901.57		$963.2832	$963.30	$963.30	$963.20