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	$176.50	12.496%	$198.5554	$198.56	$198.55	$198.60
Purchase #2	$118.46	8.706%	$128.7731	$128.77	$128.75	$128.80
Purchase #3	$57.36	3.337%	$59.2741	$59.27	$59.25	$59.30
Purchase #4	$86.41	7.441%	$92.8398	$92.84	$92.85	$92.80
Purchase #5	$213.76	3.750%	$221.776	$221.78	$221.80	$221.80
Purchase #6	$61.28	13.530%	$69.5712	$69.57	$69.55	$69.60
Purchase #7	$115.67	13.755%	$131.5804	$131.58	$131.60	$131.60
7 purchase totals =	$829.44		$902.3700	$902.37	$902.35	$902.50