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	$34.41	4.583%	$35.987	$35.99	$36.00	$36.00
Purchase #2	$184.49	10.263%	$203.4242	$203.42	$203.40	$203.40
Purchase #3	$172.54	4.240%	$179.8557	$179.86	$179.85	$179.90
Purchase #4	$185.76	7.535%	$199.757	$199.76	$199.75	$199.80
Purchase #5	$220.40	12.482%	$247.9103	$247.91	$247.90	$247.90
Purchase #6	$83.57	13.829%	$95.1269	$95.13	$95.15	$95.10
Purchase #7	$96.59	3.426%	$99.8992	$99.90	$99.90	$99.90
7 purchase totals =	$977.76		$1,061.9603	$1,061.97	$1,061.95	$1,062.00