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	$197.83	12.250%	$222.0642	$222.06	$222.05	$222.10
Purchase #2	$22.29	7.134%	$23.8802	$23.88	$23.90	$23.90
Purchase #3	$207.80	5.181%	$218.5661	$218.57	$218.55	$218.60
Purchase #4	$78.93	9.402%	$86.351	$86.35	$86.35	$86.40
Purchase #5	$167.66	10.240%	$184.8284	$184.83	$184.85	$184.80
Purchase #6	$51.57	11.520%	$57.5109	$57.51	$57.50	$57.50
Purchase #7	$156.58	10.389%	$172.8471	$172.85	$172.85	$172.80
7 purchase totals =	$882.66		$966.0479	$966.05	$966.05	$966.10