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	$82.99	4.788%	$86.9636	$86.96	$86.95	$87.00
Purchase #2	$53.58	6.514%	$57.0702	$57.07	$57.05	$57.10
Purchase #3	$178.89	3.677%	$185.4678	$185.47	$185.45	$185.50
Purchase #4	$80.37	3.665%	$83.3156	$83.32	$83.30	$83.30
Purchase #5	$183.48	7.124%	$196.5511	$196.55	$196.55	$196.60
Purchase #6	$34.65	12.183%	$38.8714	$38.87	$38.85	$38.90
Purchase #7	$210.65	8.844%	$229.2799	$229.28	$229.30	$229.30
7 purchase totals =	$824.61		$877.5196	$877.52	$877.45	$877.70