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	$124.28	13.860%	$141.5052	$141.51	$141.50	$141.50
Purchase #2	$222.48	4.656%	$232.8387	$232.84	$232.85	$232.80
Purchase #3	$47.53	11.338%	$52.919	$52.92	$52.90	$52.90
Purchase #4	$65.65	13.683%	$74.6329	$74.63	$74.65	$74.60
Purchase #5	$57.54	6.569%	$61.3198	$61.32	$61.30	$61.30
Purchase #6	$185.31	8.423%	$200.9187	$200.92	$200.90	$200.90
Purchase #7	$115.48	13.536%	$131.1114	$131.11	$131.10	$131.10
7 purchase totals =	$818.27		$895.2457	$895.25	$895.20	$895.10