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	$122.76	7.458%	$131.9154	$131.92	$131.90	$131.90
Purchase #2	$155.37	7.427%	$166.9093	$166.91	$166.90	$166.90
Purchase #3	$217.46	12.776%	$245.2427	$245.24	$245.25	$245.20
Purchase #4	$159.56	13.358%	$180.874	$180.87	$180.85	$180.90
Purchase #5	$181.69	8.175%	$196.5432	$196.54	$196.55	$196.50
Purchase #6	$196.87	6.766%	$210.1902	$210.19	$210.20	$210.20
Purchase #7	$63.97	13.212%	$72.4217	$72.42	$72.40	$72.40
7 purchase totals =	$1,097.68		$1,204.0965	$1,204.09	$1,204.05	$1,204.00