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	$241.79	9.447%	$264.6319	$264.63	$264.65	$264.60
Purchase #2	$173.73	7.870%	$187.4026	$187.40	$187.40	$187.40
Purchase #3	$109.52	12.317%	$123.0096	$123.01	$123.00	$123.00
Purchase #4	$137.43	11.345%	$153.0214	$153.02	$153.00	$153.00
Purchase #5	$82.75	12.253%	$92.8894	$92.89	$92.90	$92.90
Purchase #6	$43.92	7.598%	$47.257	$47.26	$47.25	$47.30
Purchase #7	$164.73	10.207%	$181.544	$181.54	$181.55	$181.50
7 purchase totals =	$953.87		$1,049.7559	$1,049.75	$1,049.75	$1,049.70