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	$128.73	10.264%	$141.9428	$141.94	$141.95	$141.90
Purchase #2	$132.25	8.187%	$143.0773	$143.08	$143.10	$143.10
Purchase #3	$83.59	3.787%	$86.7556	$86.76	$86.75	$86.80
Purchase #4	$72.60	13.287%	$82.2464	$82.25	$82.25	$82.20
Purchase #5	$202.59	9.222%	$221.2728	$221.27	$221.25	$221.30
Purchase #6	$84.35	4.532%	$88.1727	$88.17	$88.15	$88.20
Purchase #7	$216.76	7.495%	$233.0062	$233.01	$233.00	$233.00
7 purchase totals =	$920.87		$996.4738	$996.48	$996.45	$996.50