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	$79.37	8.791%	$86.3474	$86.35	$86.35	$86.30
Purchase #2	$10.64	13.374%	$12.063	$12.06	$12.05	$12.10
Purchase #3	$150.73	4.365%	$157.3094	$157.31	$157.30	$157.30
Purchase #4	$6.78	13.853%	$7.7192	$7.72	$7.70	$7.70
Purchase #5	$67.85	7.470%	$72.9184	$72.92	$72.90	$72.90
Purchase #6	$223.73	6.619%	$238.5387	$238.54	$238.55	$238.50
Purchase #7	$231.32	11.739%	$258.4747	$258.47	$258.45	$258.50
7 purchase totals =	$770.42		$833.3708	$833.37	$833.30	$833.30