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	$105.34	3.833%	$109.3777	$109.38	$109.40	$109.40
Purchase #2	$6.85	10.795%	$7.5895	$7.59	$7.60	$7.60
Purchase #3	$49.99	12.597%	$56.2872	$56.29	$56.30	$56.30
Purchase #4	$119.75	3.169%	$123.5449	$123.54	$123.55	$123.50
Purchase #5	$211.37	9.696%	$231.8644	$231.86	$231.85	$231.90
Purchase #6	$133.54	4.700%	$139.8164	$139.82	$139.80	$139.80
Purchase #7	$227.91	11.333%	$253.739	$253.74	$253.75	$253.70
7 purchase totals =	$854.75		$922.2191	$922.22	$922.25	$922.20