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	$31.69	3.731%	$32.8724	$32.87	$32.85	$32.90
Purchase #2	$63.48	5.267%	$66.8235	$66.82	$66.80	$66.80
Purchase #3	$184.50	8.313%	$199.8375	$199.84	$199.85	$199.80
Purchase #4	$122.93	6.315%	$130.693	$130.69	$130.70	$130.70
Purchase #5	$166.49	11.669%	$185.9177	$185.92	$185.90	$185.90
Purchase #6	$196.33	10.715%	$217.3668	$217.37	$217.35	$217.40
Purchase #7	$175.36	4.823%	$183.8176	$183.82	$183.80	$183.80
7 purchase totals =	$940.78		$1,017.3285	$1,017.33	$1,017.25	$1,017.30