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	$170.77	12.628%	$192.3348	$192.33	$192.35	$192.30
Purchase #2	$232.84	12.195%	$261.2348	$261.23	$261.25	$261.20
Purchase #3	$240.33	10.636%	$265.8915	$265.89	$265.90	$265.90
Purchase #4	$84.81	8.666%	$92.1596	$92.16	$92.15	$92.20
Purchase #5	$67.28	13.741%	$76.5249	$76.52	$76.50	$76.50
Purchase #6	$178.96	9.786%	$196.473	$196.47	$196.45	$196.50
Purchase #7	$175.69	8.350%	$190.3601	$190.36	$190.35	$190.40
7 purchase totals =	$1,150.68		$1,274.9787	$1,274.96	$1,274.95	$1,275.00