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	$155.89	12.539%	$175.437	$175.44	$175.45	$175.40
Purchase #2	$204.33	8.794%	$222.2988	$222.30	$222.30	$222.30
Purchase #3	$233.88	13.693%	$265.9052	$265.91	$265.90	$265.90
Purchase #4	$146.75	13.387%	$166.3954	$166.40	$166.40	$166.40
Purchase #5	$95.78	13.184%	$108.4076	$108.41	$108.40	$108.40
Purchase #6	$122.94	7.256%	$131.8605	$131.86	$131.85	$131.90
Purchase #7	$144.56	12.842%	$163.1244	$163.12	$163.10	$163.10
7 purchase totals =	$1,104.13		$1,233.4289	$1,233.44	$1,233.40	$1,233.40