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	$197.35	12.740%	$222.4924	$222.49	$222.50	$222.50
Purchase #2	$82.71	8.133%	$89.4368	$89.44	$89.45	$89.40
Purchase #3	$190.66	4.660%	$199.5448	$199.54	$199.55	$199.50
Purchase #4	$117.99	3.831%	$122.5102	$122.51	$122.50	$122.50
Purchase #5	$170.72	5.115%	$179.4523	$179.45	$179.45	$179.50
Purchase #6	$184.95	10.247%	$203.9018	$203.90	$203.90	$203.90
Purchase #7	$150.67	11.861%	$168.541	$168.54	$168.55	$168.50
7 purchase totals =	$1,095.05		$1,185.8793	$1,185.87	$1,185.90	$1,185.80