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	$61.66	12.613%	$69.4372	$69.44	$69.45	$69.40
Purchase #2	$173.87	4.720%	$182.0767	$182.08	$182.10	$182.10
Purchase #3	$195.31	7.855%	$210.6516	$210.65	$210.65	$210.70
Purchase #4	$164.42	12.730%	$185.3507	$185.35	$185.35	$185.40
Purchase #5	$186.56	6.377%	$198.4569	$198.46	$198.45	$198.50
Purchase #6	$39.30	8.729%	$42.7305	$42.73	$42.75	$42.70
Purchase #7	$209.51	3.578%	$217.0063	$217.01	$217.00	$217.00
7 purchase totals =	$1,030.63		$1,105.7099	$1,105.72	$1,105.75	$1,105.80