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	$40.73	12.804%	$45.9451	$45.95	$45.95	$45.90
Purchase #2	$35.55	4.638%	$37.1988	$37.20	$37.20	$37.20
Purchase #3	$143.80	7.469%	$154.5404	$154.54	$154.55	$154.50
Purchase #4	$78.76	13.571%	$89.4485	$89.45	$89.45	$89.40
Purchase #5	$121.57	5.174%	$127.86	$127.86	$127.85	$127.90
Purchase #6	$7.51	10.590%	$8.3053	$8.31	$8.30	$8.30
Purchase #7	$238.55	6.227%	$253.4045	$253.40	$253.40	$253.40
7 purchase totals =	$666.47		$716.7026	$716.71	$716.70	$716.60