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	$87.98	12.606%	$99.0708	$99.07	$99.05	$99.10
Purchase #2	$100.71	3.174%	$103.9065	$103.91	$103.90	$103.90
Purchase #3	$162.47	10.429%	$179.414	$179.41	$179.40	$179.40
Purchase #4	$225.35	13.380%	$255.5018	$255.50	$255.50	$255.50
Purchase #5	$207.32	8.319%	$224.567	$224.57	$224.55	$224.60
Purchase #6	$150.47	13.633%	$170.9836	$170.98	$171.00	$171.00
Purchase #7	$205.95	12.185%	$231.045	$231.05	$231.05	$231.00
7 purchase totals =	$1,140.25		$1,264.4887	$1,264.49	$1,264.45	$1,264.50