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	$130.96	10.631%	$144.8824	$144.88	$144.90	$144.90
Purchase #2	$64.79	12.444%	$72.8525	$72.85	$72.85	$72.90
Purchase #3	$28.67	9.778%	$31.4734	$31.47	$31.45	$31.50
Purchase #4	$176.37	5.457%	$185.9945	$185.99	$186.00	$186.00
Purchase #5	$128.44	8.714%	$139.6323	$139.63	$139.65	$139.60
Purchase #6	$85.72	9.479%	$93.8454	$93.85	$93.85	$93.80
Purchase #7	$118.34	11.167%	$131.555	$131.56	$131.55	$131.60
7 purchase totals =	$733.29		$800.2355	$800.23	$800.25	$800.30