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	$120.78	3.696%	$125.244	$125.24	$125.25	$125.20
Purchase #2	$192.51	13.358%	$218.2255	$218.23	$218.25	$218.20
Purchase #3	$151.56	5.459%	$159.8337	$159.83	$159.85	$159.80
Purchase #4	$208.40	6.699%	$222.3607	$222.36	$222.35	$222.40
Purchase #5	$211.78	7.132%	$226.8841	$226.88	$226.90	$226.90
Purchase #6	$48.25	9.469%	$52.8188	$52.82	$52.80	$52.80
Purchase #7	$19.29	4.620%	$20.1812	$20.18	$20.20	$20.20
7 purchase totals =	$952.57		$1,025.5480	$1,025.54	$1,025.60	$1,025.50