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	$232.25	7.187%	$248.9418	$248.94	$248.95	$248.90
Purchase #2	$198.51	12.107%	$222.5436	$222.54	$222.55	$222.50
Purchase #3	$41.28	9.525%	$45.2119	$45.21	$45.20	$45.20
Purchase #4	$108.71	13.475%	$123.3587	$123.36	$123.35	$123.40
Purchase #5	$137.49	12.269%	$154.3586	$154.36	$154.35	$154.40
Purchase #6	$176.78	4.358%	$184.4841	$184.48	$184.50	$184.50
Purchase #7	$172.31	11.179%	$191.5725	$191.57	$191.55	$191.60
7 purchase totals =	$1,067.33		$1,170.4712	$1,170.46	$1,170.45	$1,170.50