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	$87.37	4.702%	$91.4781	$91.48	$91.50	$91.50
Purchase #2	$40.53	5.191%	$42.6339	$42.63	$42.65	$42.60
Purchase #3	$81.29	7.193%	$87.1372	$87.14	$87.15	$87.10
Purchase #4	$141.70	6.166%	$150.4372	$150.44	$150.45	$150.40
Purchase #5	$130.68	9.759%	$143.4331	$143.43	$143.45	$143.40
Purchase #6	$130.67	9.255%	$142.7635	$142.76	$142.75	$142.80
Purchase #7	$201.81	11.263%	$224.5399	$224.54	$224.55	$224.50
7 purchase totals =	$814.05		$882.4229	$882.42	$882.50	$882.30