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	$210.40	5.705%	$222.4033	$222.40	$222.40	$222.40
Purchase #2	$72.56	11.548%	$80.9392	$80.94	$80.95	$80.90
Purchase #3	$141.50	12.293%	$158.8946	$158.89	$158.90	$158.90
Purchase #4	$241.33	10.674%	$267.0896	$267.09	$267.10	$267.10
Purchase #5	$29.92	4.752%	$31.3418	$31.34	$31.35	$31.30
Purchase #6	$158.97	6.442%	$169.2108	$169.21	$169.20	$169.20
Purchase #7	$175.48	12.537%	$197.4799	$197.48	$197.50	$197.50
7 purchase totals =	$1,030.16		$1,127.3592	$1,127.35	$1,127.40	$1,127.30