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	$61.88	8.380%	$67.0655	$67.07	$67.05	$67.10
Purchase #2	$248.97	11.443%	$277.4596	$277.46	$277.45	$277.50
Purchase #3	$46.83	13.484%	$53.1446	$53.14	$53.15	$53.10
Purchase #4	$79.47	7.322%	$85.2888	$85.29	$85.30	$85.30
Purchase #5	$45.34	7.639%	$48.8035	$48.80	$48.80	$48.80
Purchase #6	$93.94	5.828%	$99.4148	$99.41	$99.40	$99.40
Purchase #7	$10.98	6.247%	$11.6659	$11.67	$11.65	$11.70
7 purchase totals =	$587.41		$642.8427	$642.84	$642.80	$642.90