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	$128.87	10.111%	$141.9	$141.90	$141.90	$141.90
Purchase #2	$237.60	3.709%	$246.4126	$246.41	$246.40	$246.40
Purchase #3	$22.86	7.546%	$24.585	$24.59	$24.60	$24.60
Purchase #4	$240.88	5.457%	$254.0248	$254.02	$254.00	$254.00
Purchase #5	$38.54	11.140%	$42.8334	$42.83	$42.85	$42.80
Purchase #6	$58.93	10.317%	$65.0098	$65.01	$65.00	$65.00
Purchase #7	$217.31	5.763%	$229.8336	$229.83	$229.85	$229.80
7 purchase totals =	$944.99		$1,004.5992	$1,004.59	$1,004.60	$1,004.50