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	$134.61	5.141%	$141.5303	$141.53	$141.55	$141.50
Purchase #2	$114.41	11.665%	$127.7559	$127.76	$127.75	$127.80
Purchase #3	$158.59	11.124%	$176.2316	$176.23	$176.25	$176.20
Purchase #4	$59.86	5.493%	$63.1481	$63.15	$63.15	$63.10
Purchase #5	$159.37	8.226%	$172.4798	$172.48	$172.50	$172.50
Purchase #6	$76.96	9.820%	$84.5175	$84.52	$84.50	$84.50
Purchase #7	$28.69	8.119%	$31.0193	$31.02	$31.00	$31.00
7 purchase totals =	$732.49		$796.6825	$796.69	$796.70	$796.60