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	$161.78	11.501%	$180.3863	$180.39	$180.40	$180.40
Purchase #2	$53.47	11.874%	$59.819	$59.82	$59.80	$59.80
Purchase #3	$111.44	3.274%	$115.0885	$115.09	$115.10	$115.10
Purchase #4	$154.99	9.372%	$169.5157	$169.52	$169.50	$169.50
Purchase #5	$75.55	13.417%	$85.6865	$85.69	$85.70	$85.70
Purchase #6	$190.60	11.119%	$211.7928	$211.79	$211.80	$211.80
Purchase #7	$193.29	12.232%	$216.9332	$216.93	$216.95	$216.90
7 purchase totals =	$941.12		$1,039.2220	$1,039.23	$1,039.25	$1,039.20