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	$172.40	3.389%	$178.2426	$178.24	$178.25	$178.20
Purchase #2	$233.76	3.697%	$242.4021	$242.40	$242.40	$242.40
Purchase #3	$174.94	10.179%	$192.7471	$192.75	$192.75	$192.70
Purchase #4	$184.86	4.561%	$193.2915	$193.29	$193.30	$193.30
Purchase #5	$121.48	8.767%	$132.1302	$132.13	$132.15	$132.10
Purchase #6	$82.57	3.426%	$85.3988	$85.40	$85.40	$85.40
Purchase #7	$94.32	9.722%	$103.4898	$103.49	$103.50	$103.50
7 purchase totals =	$1,064.33		$1,127.7021	$1,127.70	$1,127.75	$1,127.60