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	$109.46	3.589%	$113.3885	$113.39	$113.40	$113.40
Purchase #2	$36.51	11.351%	$40.6543	$40.65	$40.65	$40.70
Purchase #3	$179.67	9.188%	$196.1781	$196.18	$196.20	$196.20
Purchase #4	$163.65	4.533%	$171.0683	$171.07	$171.05	$171.10
Purchase #5	$101.27	3.611%	$104.9269	$104.93	$104.95	$104.90
Purchase #6	$212.43	5.830%	$224.8147	$224.81	$224.80	$224.80
Purchase #7	$31.58	7.385%	$33.9122	$33.91	$33.90	$33.90
7 purchase totals =	$834.57		$884.9430	$884.94	$884.95	$885.00