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	$248.94	5.604%	$262.8906	$262.89	$262.90	$262.90
Purchase #2	$141.52	4.792%	$148.3016	$148.30	$148.30	$148.30
Purchase #3	$211.94	12.535%	$238.5067	$238.51	$238.50	$238.50
Purchase #4	$158.94	10.551%	$175.7098	$175.71	$175.70	$175.70
Purchase #5	$214.82	11.719%	$239.9948	$239.99	$240.00	$240.00
Purchase #6	$67.76	5.714%	$71.6318	$71.63	$71.65	$71.60
Purchase #7	$37.95	12.610%	$42.7355	$42.74	$42.75	$42.70
7 purchase totals =	$1,081.87		$1,179.7708	$1,179.77	$1,179.80	$1,179.70