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	$125.41	5.663%	$132.512	$132.51	$132.50	$132.50
Purchase #2	$103.44	6.675%	$110.3446	$110.34	$110.35	$110.30
Purchase #3	$169.53	7.617%	$182.4431	$182.44	$182.45	$182.40
Purchase #4	$158.87	3.282%	$164.0841	$164.08	$164.10	$164.10
Purchase #5	$78.89	5.222%	$83.0096	$83.01	$83.00	$83.00
Purchase #6	$107.52	8.769%	$116.9484	$116.95	$116.95	$116.90
Purchase #7	$134.72	12.859%	$152.0436	$152.04	$152.05	$152.00
7 purchase totals =	$878.38		$941.3854	$941.37	$941.40	$941.20