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	$50.46	3.281%	$52.1156	$52.12	$52.10	$52.10
Purchase #2	$234.61	11.464%	$261.5057	$261.51	$261.50	$261.50
Purchase #3	$11.35	9.495%	$12.4277	$12.43	$12.45	$12.40
Purchase #4	$136.89	11.686%	$152.887	$152.89	$152.90	$152.90
Purchase #5	$86.40	3.396%	$89.3341	$89.33	$89.35	$89.30
Purchase #6	$230.36	4.397%	$240.4889	$240.49	$240.50	$240.50
Purchase #7	$131.43	10.666%	$145.4483	$145.45	$145.45	$145.40
7 purchase totals =	$881.50		$954.2073	$954.22	$954.25	$954.10