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	$77.33	7.152%	$82.8606	$82.86	$82.85	$82.90
Purchase #2	$226.66	3.152%	$233.8043	$233.80	$233.80	$233.80
Purchase #3	$172.45	4.473%	$180.1637	$180.16	$180.15	$180.20
Purchase #4	$74.72	12.281%	$83.8964	$83.90	$83.90	$83.90
Purchase #5	$108.68	8.559%	$117.9819	$117.98	$118.00	$118.00
Purchase #6	$240.25	13.867%	$273.5655	$273.57	$273.55	$273.60
Purchase #7	$29.96	7.239%	$32.1288	$32.13	$32.15	$32.10
7 purchase totals =	$930.05		$1,004.4012	$1,004.40	$1,004.40	$1,004.50