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	$198.30	6.837%	$211.8578	$211.86	$211.85	$211.90
Purchase #2	$59.90	4.394%	$62.532	$62.53	$62.55	$62.50
Purchase #3	$109.77	12.323%	$123.297	$123.30	$123.30	$123.30
Purchase #4	$49.64	12.127%	$55.6598	$55.66	$55.65	$55.70
Purchase #5	$62.67	7.503%	$67.3721	$67.37	$67.35	$67.40
Purchase #6	$161.84	7.182%	$173.4633	$173.46	$173.45	$173.50
Purchase #7	$192.59	13.467%	$218.5261	$218.53	$218.55	$218.50
7 purchase totals =	$834.71		$912.7081	$912.71	$912.70	$912.80