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	$111.90	5.149%	$117.6617	$117.66	$117.65	$117.70
Purchase #2	$192.38	12.185%	$215.8215	$215.82	$215.80	$215.80
Purchase #3	$78.58	6.512%	$83.6971	$83.70	$83.70	$83.70
Purchase #4	$152.43	12.676%	$171.752	$171.75	$171.75	$171.80
Purchase #5	$94.36	6.302%	$100.3066	$100.31	$100.30	$100.30
Purchase #6	$102.50	4.173%	$106.7773	$106.78	$106.80	$106.80
Purchase #7	$120.68	9.727%	$132.4185	$132.42	$132.40	$132.40
7 purchase totals =	$852.83		$928.4347	$928.44	$928.40	$928.50