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	$97.63	7.548%	$104.9991	$105.00	$105.00	$105.00
Purchase #2	$120.56	9.799%	$132.3737	$132.37	$132.35	$132.40
Purchase #3	$197.97	7.458%	$212.7346	$212.73	$212.75	$212.70
Purchase #4	$123.98	12.833%	$139.8904	$139.89	$139.90	$139.90
Purchase #5	$154.87	6.133%	$164.3682	$164.37	$164.35	$164.40
Purchase #6	$32.39	4.778%	$33.9376	$33.94	$33.95	$33.90
Purchase #7	$50.43	7.628%	$54.2768	$54.28	$54.30	$54.30
7 purchase totals =	$777.83		$842.5804	$842.58	$842.60	$842.60