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	$180.97	8.516%	$196.3814	$196.38	$196.40	$196.40
Purchase #2	$185.30	4.833%	$194.2555	$194.26	$194.25	$194.30
Purchase #3	$14.47	11.218%	$16.0932	$16.09	$16.10	$16.10
Purchase #4	$142.73	9.357%	$156.0852	$156.09	$156.10	$156.10
Purchase #5	$115.58	13.739%	$131.4595	$131.46	$131.45	$131.50
Purchase #6	$163.70	5.406%	$172.5496	$172.55	$172.55	$172.50
Purchase #7	$36.55	3.767%	$37.9268	$37.93	$37.95	$37.90
7 purchase totals =	$839.30		$904.7512	$904.76	$904.80	$904.80