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	$102.31	3.745%	$106.1415	$106.14	$106.15	$106.10
Purchase #2	$170.32	5.240%	$179.2448	$179.24	$179.25	$179.20
Purchase #3	$62.82	11.308%	$69.9237	$69.92	$69.90	$69.90
Purchase #4	$108.89	13.698%	$123.8058	$123.81	$123.80	$123.80
Purchase #5	$34.34	8.859%	$37.3822	$37.38	$37.40	$37.40
Purchase #6	$241.96	12.612%	$272.476	$272.48	$272.50	$272.50
Purchase #7	$91.62	5.364%	$96.5345	$96.53	$96.55	$96.50
7 purchase totals =	$812.26		$885.5085	$885.50	$885.55	$885.40