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	$170.47	11.259%	$189.6632	$189.66	$189.65	$189.70
Purchase #2	$207.40	7.739%	$223.4507	$223.45	$223.45	$223.50
Purchase #3	$240.78	13.601%	$273.5285	$273.53	$273.55	$273.50
Purchase #4	$179.43	9.628%	$196.7055	$196.71	$196.70	$196.70
Purchase #5	$16.46	10.104%	$18.1231	$18.12	$18.10	$18.10
Purchase #6	$18.96	10.153%	$20.885	$20.89	$20.90	$20.90
Purchase #7	$113.79	6.730%	$121.4481	$121.45	$121.45	$121.40
7 purchase totals =	$947.29		$1,043.8041	$1,043.81	$1,043.80	$1,043.80