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	$248.32	5.231%	$261.3096	$261.31	$261.30	$261.30
Purchase #2	$240.27	6.478%	$255.8347	$255.83	$255.85	$255.80
Purchase #3	$120.28	8.484%	$130.4846	$130.48	$130.50	$130.50
Purchase #4	$84.63	10.448%	$93.4721	$93.47	$93.45	$93.50
Purchase #5	$174.84	7.448%	$187.8621	$187.86	$187.85	$187.90
Purchase #6	$37.78	8.384%	$40.9475	$40.95	$40.95	$40.90
Purchase #7	$41.89	8.464%	$45.4356	$45.44	$45.45	$45.40
7 purchase totals =	$948.01		$1,015.3462	$1,015.34	$1,015.35	$1,015.30