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	$215.34	8.560%	$233.7731	$233.77	$233.75	$233.80
Purchase #2	$208.30	12.189%	$233.6897	$233.69	$233.70	$233.70
Purchase #3	$127.77	7.722%	$137.6364	$137.64	$137.65	$137.60
Purchase #4	$130.44	8.757%	$141.8626	$141.86	$141.85	$141.90
Purchase #5	$245.32	4.671%	$256.7789	$256.78	$256.80	$256.80
Purchase #6	$98.95	11.430%	$110.26	$110.26	$110.25	$110.30
Purchase #7	$131.69	5.868%	$139.4176	$139.42	$139.40	$139.40
7 purchase totals =	$1,157.81		$1,253.4183	$1,253.42	$1,253.40	$1,253.50