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	$174.86	5.736%	$184.89	$184.89	$184.90	$184.90
Purchase #2	$122.46	7.285%	$131.3812	$131.38	$131.40	$131.40
Purchase #3	$36.69	4.121%	$38.202	$38.20	$38.20	$38.20
Purchase #4	$43.60	4.645%	$45.6252	$45.63	$45.65	$45.60
Purchase #5	$164.49	10.820%	$182.2878	$182.29	$182.30	$182.30
Purchase #6	$241.27	13.791%	$274.5435	$274.54	$274.55	$274.50
Purchase #7	$208.88	10.801%	$231.4411	$231.44	$231.45	$231.40
7 purchase totals =	$992.25		$1,088.3708	$1,088.37	$1,088.45	$1,088.30