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	$89.59	12.112%	$100.4411	$100.44	$100.45	$100.40
Purchase #2	$66.87	6.201%	$71.0166	$71.02	$71.00	$71.00
Purchase #3	$210.83	4.479%	$220.2731	$220.27	$220.25	$220.30
Purchase #4	$230.62	10.547%	$254.9435	$254.94	$254.95	$254.90
Purchase #5	$100.66	7.309%	$108.0172	$108.02	$108.00	$108.00
Purchase #6	$141.80	5.818%	$150.0499	$150.05	$150.05	$150.00
Purchase #7	$33.99	11.372%	$37.8553	$37.86	$37.85	$37.90
7 purchase totals =	$874.36		$942.5967	$942.60	$942.55	$942.50