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	$127.50	7.325%	$136.8394	$136.84	$136.85	$136.80
Purchase #2	$93.92	6.183%	$99.7271	$99.73	$99.75	$99.70
Purchase #3	$198.58	4.220%	$206.9601	$206.96	$206.95	$207.00
Purchase #4	$146.97	4.357%	$153.3735	$153.37	$153.35	$153.40
Purchase #5	$83.50	9.392%	$91.3423	$91.34	$91.35	$91.30
Purchase #6	$155.62	10.831%	$172.4752	$172.48	$172.50	$172.50
Purchase #7	$162.72	10.366%	$179.5876	$179.59	$179.60	$179.60
7 purchase totals =	$968.81		$1,040.3052	$1,040.31	$1,040.35	$1,040.30