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	$220.29	10.283%	$242.9424	$242.94	$242.95	$242.90
Purchase #2	$37.96	11.392%	$42.2844	$42.28	$42.30	$42.30
Purchase #3	$78.32	5.693%	$82.7788	$82.78	$82.80	$82.80
Purchase #4	$32.41	9.273%	$35.4154	$35.42	$35.40	$35.40
Purchase #5	$228.69	10.422%	$252.5241	$252.52	$252.50	$252.50
Purchase #6	$198.64	11.398%	$221.281	$221.28	$221.30	$221.30
Purchase #7	$234.77	12.692%	$264.567	$264.57	$264.55	$264.60
7 purchase totals =	$1,031.08		$1,141.7931	$1,141.79	$1,141.80	$1,141.80