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	$30.64	12.313%	$34.4127	$34.41	$34.40	$34.40
Purchase #2	$202.65	5.376%	$213.5445	$213.54	$213.55	$213.50
Purchase #3	$222.46	12.112%	$249.4044	$249.40	$249.40	$249.40
Purchase #4	$187.78	8.527%	$203.792	$203.79	$203.80	$203.80
Purchase #5	$81.50	11.527%	$90.8945	$90.89	$90.90	$90.90
Purchase #6	$182.36	4.516%	$190.5954	$190.60	$190.60	$190.60
Purchase #7	$144.47	13.777%	$164.3736	$164.37	$164.35	$164.40
7 purchase totals =	$1,051.86		$1,147.0171	$1,147.00	$1,147.00	$1,147.00