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	$195.43	9.865%	$214.7092	$214.71	$214.70	$214.70
Purchase #2	$95.89	8.872%	$104.3974	$104.40	$104.40	$104.40
Purchase #3	$49.78	7.644%	$53.5852	$53.59	$53.60	$53.60
Purchase #4	$88.51	12.289%	$99.387	$99.39	$99.40	$99.40
Purchase #5	$90.80	7.796%	$97.8788	$97.88	$97.90	$97.90
Purchase #6	$38.95	9.577%	$42.6802	$42.68	$42.70	$42.70
Purchase #7	$14.53	12.241%	$16.3086	$16.31	$16.30	$16.30
7 purchase totals =	$573.89		$628.9464	$628.96	$629.00	$629.00