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	$30.62	8.819%	$33.3204	$33.32	$33.30	$33.30
Purchase #2	$247.76	12.303%	$278.2419	$278.24	$278.25	$278.20
Purchase #3	$87.41	8.108%	$94.4972	$94.50	$94.50	$94.50
Purchase #4	$38.40	11.842%	$42.9473	$42.95	$42.95	$42.90
Purchase #5	$39.77	3.450%	$41.1421	$41.14	$41.15	$41.10
Purchase #6	$47.90	8.516%	$51.9792	$51.98	$52.00	$52.00
Purchase #7	$69.83	3.246%	$72.0967	$72.10	$72.10	$72.10
7 purchase totals =	$561.69		$614.2248	$614.23	$614.25	$614.10