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	$244.31	7.430%	$262.4622	$262.46	$262.45	$262.50
Purchase #2	$39.47	6.399%	$41.9957	$42.00	$42.00	$42.00
Purchase #3	$136.93	13.527%	$155.4525	$155.45	$155.45	$155.50
Purchase #4	$137.39	6.143%	$145.8299	$145.83	$145.85	$145.80
Purchase #5	$238.91	12.554%	$268.9028	$268.90	$268.90	$268.90
Purchase #6	$88.77	4.261%	$92.5525	$92.55	$92.55	$92.60
Purchase #7	$226.82	13.214%	$256.792	$256.79	$256.80	$256.80
7 purchase totals =	$1,112.60		$1,223.9876	$1,223.98	$1,224.00	$1,224.10