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	$217.63	13.371%	$246.7293	$246.73	$246.75	$246.70
Purchase #2	$200.80	12.801%	$226.5044	$226.50	$226.50	$226.50
Purchase #3	$156.88	5.631%	$165.7139	$165.71	$165.70	$165.70
Purchase #4	$57.44	3.435%	$59.4131	$59.41	$59.40	$59.40
Purchase #5	$210.32	13.380%	$238.4608	$238.46	$238.45	$238.50
Purchase #6	$113.53	4.397%	$118.5219	$118.52	$118.50	$118.50
Purchase #7	$97.36	9.440%	$106.5508	$106.55	$106.55	$106.60
7 purchase totals =	$1,053.96		$1,161.8942	$1,161.88	$1,161.85	$1,161.90