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	$212.56	4.218%	$221.5258	$221.53	$221.55	$221.50
Purchase #2	$221.93	5.679%	$234.5334	$234.53	$234.55	$234.50
Purchase #3	$28.47	8.241%	$30.8162	$30.82	$30.80	$30.80
Purchase #4	$183.63	13.441%	$208.3117	$208.31	$208.30	$208.30
Purchase #5	$37.58	12.408%	$42.2429	$42.24	$42.25	$42.20
Purchase #6	$95.48	4.670%	$99.9389	$99.94	$99.95	$99.90
Purchase #7	$44.54	8.465%	$48.3103	$48.31	$48.30	$48.30
7 purchase totals =	$824.19		$885.6792	$885.68	$885.70	$885.50