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	$124.70	7.801%	$134.4278	$134.43	$134.45	$134.40
Purchase #2	$152.70	6.293%	$162.3094	$162.31	$162.30	$162.30
Purchase #3	$39.39	6.549%	$41.9697	$41.97	$41.95	$42.00
Purchase #4	$108.65	3.814%	$112.7939	$112.79	$112.80	$112.80
Purchase #5	$52.39	13.466%	$59.4448	$59.44	$59.45	$59.40
Purchase #6	$55.27	3.368%	$57.1315	$57.13	$57.15	$57.10
Purchase #7	$235.92	11.698%	$263.5179	$263.52	$263.50	$263.50
7 purchase totals =	$769.02		$831.5950	$831.59	$831.60	$831.50