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	$134.51	8.145%	$145.4658	$145.47	$145.45	$145.50
Purchase #2	$204.81	13.220%	$231.8859	$231.89	$231.90	$231.90
Purchase #3	$166.53	12.814%	$187.8692	$187.87	$187.85	$187.90
Purchase #4	$202.44	9.720%	$222.1172	$222.12	$222.10	$222.10
Purchase #5	$174.85	6.291%	$185.8498	$185.85	$185.85	$185.80
Purchase #6	$240.93	4.379%	$251.4803	$251.48	$251.50	$251.50
Purchase #7	$131.31	11.711%	$146.6877	$146.69	$146.70	$146.70
7 purchase totals =	$1,255.38		$1,371.3559	$1,371.37	$1,371.35	$1,371.40