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	$78.88	11.344%	$87.8281	$87.83	$87.85	$87.80
Purchase #2	$16.81	4.715%	$17.6026	$17.60	$17.60	$17.60
Purchase #3	$20.29	11.791%	$22.6824	$22.68	$22.70	$22.70
Purchase #4	$75.66	3.820%	$78.5502	$78.55	$78.55	$78.60
Purchase #5	$62.59	10.215%	$68.9836	$68.98	$69.00	$69.00
Purchase #6	$62.58	7.562%	$67.3123	$67.31	$67.30	$67.30
Purchase #7	$158.60	13.793%	$180.4757	$180.48	$180.50	$180.50
7 purchase totals =	$475.41		$523.4349	$523.43	$523.50	$523.50