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	$60.47	12.148%	$67.8159	$67.82	$67.80	$67.80
Purchase #2	$39.68	5.480%	$41.8545	$41.85	$41.85	$41.90
Purchase #3	$16.70	9.212%	$18.2384	$18.24	$18.25	$18.20
Purchase #4	$43.64	10.617%	$48.2733	$48.27	$48.25	$48.30
Purchase #5	$211.81	10.429%	$233.8997	$233.90	$233.90	$233.90
Purchase #6	$96.63	4.803%	$101.2711	$101.27	$101.25	$101.30
Purchase #7	$14.94	6.756%	$15.9493	$15.95	$15.95	$15.90
7 purchase totals =	$483.87		$527.3022	$527.30	$527.25	$527.30