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	$155.64	10.526%	$172.0227	$172.02	$172.00	$172.00
Purchase #2	$136.33	5.247%	$143.4832	$143.48	$143.50	$143.50
Purchase #3	$215.30	3.666%	$223.1929	$223.19	$223.20	$223.20
Purchase #4	$110.70	6.188%	$117.5501	$117.55	$117.55	$117.60
Purchase #5	$95.78	8.561%	$103.9797	$103.98	$104.00	$104.00
Purchase #6	$78.30	7.639%	$84.2813	$84.28	$84.30	$84.30
Purchase #7	$81.33	11.364%	$90.5723	$90.57	$90.55	$90.60
7 purchase totals =	$873.38		$935.0822	$935.07	$935.10	$935.20