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	$121.95	8.788%	$132.667	$132.67	$132.65	$132.70
Purchase #2	$229.32	13.522%	$260.3287	$260.33	$260.35	$260.30
Purchase #3	$30.68	13.435%	$34.8019	$34.80	$34.80	$34.80
Purchase #4	$250.94	5.568%	$264.9123	$264.91	$264.90	$264.90
Purchase #5	$52.84	13.377%	$59.9084	$59.91	$59.90	$59.90
Purchase #6	$40.46	3.820%	$42.0056	$42.01	$42.00	$42.00
Purchase #7	$84.30	5.406%	$88.8573	$88.86	$88.85	$88.90
7 purchase totals =	$810.49		$883.4812	$883.49	$883.45	$883.50