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	$192.66	7.162%	$206.4583	$206.46	$206.45	$206.50
Purchase #2	$92.78	11.566%	$103.5109	$103.51	$103.50	$103.50
Purchase #3	$193.75	12.461%	$217.8932	$217.89	$217.90	$217.90
Purchase #4	$7.36	5.295%	$7.7497	$7.75	$7.75	$7.70
Purchase #5	$6.65	13.794%	$7.5673	$7.57	$7.55	$7.60
Purchase #6	$112.92	4.227%	$117.6931	$117.69	$117.70	$117.70
Purchase #7	$200.78	11.508%	$223.8858	$223.89	$223.90	$223.90
7 purchase totals =	$806.90		$884.7583	$884.76	$884.75	$884.80