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	$174.33	6.379%	$185.4505	$185.45	$185.45	$185.50
Purchase #2	$193.40	6.597%	$206.1586	$206.16	$206.15	$206.20
Purchase #3	$149.88	5.198%	$157.6708	$157.67	$157.65	$157.70
Purchase #4	$38.32	13.317%	$43.4231	$43.42	$43.40	$43.40
Purchase #5	$250.32	5.842%	$264.9437	$264.94	$264.95	$264.90
Purchase #6	$77.42	11.703%	$86.4805	$86.48	$86.50	$86.50
Purchase #7	$31.40	4.558%	$32.8312	$32.83	$32.85	$32.80
7 purchase totals =	$915.07		$976.9584	$976.95	$976.95	$977.00