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	$231.73	12.432%	$260.5387	$260.54	$260.55	$260.50
Purchase #2	$161.28	3.840%	$167.4732	$167.47	$167.45	$167.50
Purchase #3	$233.32	10.114%	$256.918	$256.92	$256.90	$256.90
Purchase #4	$214.30	7.630%	$230.6511	$230.65	$230.65	$230.70
Purchase #5	$210.72	6.274%	$223.9406	$223.94	$223.95	$223.90
Purchase #6	$57.73	6.450%	$61.4536	$61.45	$61.45	$61.50
Purchase #7	$190.33	4.337%	$198.5846	$198.58	$198.60	$198.60
7 purchase totals =	$1,299.41		$1,399.5598	$1,399.55	$1,399.55	$1,399.60