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	$165.50	7.209%	$177.4309	$177.43	$177.45	$177.40
Purchase #2	$47.78	10.150%	$52.6297	$52.63	$52.65	$52.60
Purchase #3	$107.74	6.655%	$114.9101	$114.91	$114.90	$114.90
Purchase #4	$177.86	10.213%	$196.0248	$196.02	$196.00	$196.00
Purchase #5	$39.46	7.655%	$42.4807	$42.48	$42.50	$42.50
Purchase #6	$97.90	9.842%	$107.5353	$107.54	$107.55	$107.50
Purchase #7	$72.86	13.194%	$82.4731	$82.47	$82.45	$82.50
7 purchase totals =	$709.10		$773.4846	$773.48	$773.50	$773.40