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	$247.89	7.652%	$266.8585	$266.86	$266.85	$266.90
Purchase #2	$62.51	13.435%	$70.9082	$70.91	$70.90	$70.90
Purchase #3	$190.72	8.336%	$206.6184	$206.62	$206.60	$206.60
Purchase #4	$30.26	10.499%	$33.437	$33.44	$33.45	$33.40
Purchase #5	$212.78	13.677%	$241.8819	$241.88	$241.90	$241.90
Purchase #6	$41.64	3.138%	$42.9467	$42.95	$42.95	$42.90
Purchase #7	$82.37	10.632%	$91.1276	$91.13	$91.15	$91.10
7 purchase totals =	$868.17		$953.7783	$953.79	$953.80	$953.70