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	$132.26	9.178%	$144.3988	$144.40	$144.40	$144.40
Purchase #2	$47.50	5.644%	$50.1809	$50.18	$50.20	$50.20
Purchase #3	$132.33	8.421%	$143.4735	$143.47	$143.45	$143.50
Purchase #4	$233.86	13.412%	$265.2253	$265.23	$265.25	$265.20
Purchase #5	$154.58	10.509%	$170.8248	$170.82	$170.80	$170.80
Purchase #6	$164.90	7.179%	$176.7382	$176.74	$176.75	$176.70
Purchase #7	$101.91	7.377%	$109.4279	$109.43	$109.45	$109.40
7 purchase totals =	$967.34		$1,060.2694	$1,060.27	$1,060.30	$1,060.20