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	$112.54	6.153%	$119.4646	$119.46	$119.45	$119.50
Purchase #2	$190.37	3.309%	$196.6693	$196.67	$196.65	$196.70
Purchase #3	$16.59	13.494%	$18.8287	$18.83	$18.85	$18.80
Purchase #4	$63.33	7.537%	$68.1032	$68.10	$68.10	$68.10
Purchase #5	$109.32	8.374%	$118.4745	$118.47	$118.45	$118.50
Purchase #6	$180.89	10.672%	$200.1946	$200.19	$200.20	$200.20
Purchase #7	$193.28	13.805%	$219.9623	$219.96	$219.95	$220.00
7 purchase totals =	$866.32		$941.6972	$941.68	$941.65	$941.80