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	$176.48	11.241%	$196.3181	$196.32	$196.30	$196.30
Purchase #2	$117.48	3.480%	$121.5683	$121.57	$121.55	$121.60
Purchase #3	$9.95	3.365%	$10.2848	$10.28	$10.30	$10.30
Purchase #4	$174.39	11.545%	$194.5233	$194.52	$194.50	$194.50
Purchase #5	$117.45	13.672%	$133.5078	$133.51	$133.50	$133.50
Purchase #6	$32.96	5.363%	$34.7276	$34.73	$34.75	$34.70
Purchase #7	$80.48	11.239%	$89.5251	$89.53	$89.55	$89.50
7 purchase totals =	$709.19		$780.4550	$780.46	$780.45	$780.40