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	$127.61	4.182%	$132.9467	$132.95	$132.95	$132.90
Purchase #2	$175.81	4.465%	$183.6599	$183.66	$183.65	$183.70
Purchase #3	$73.86	12.213%	$82.8805	$82.88	$82.90	$82.90
Purchase #4	$30.89	11.791%	$34.5322	$34.53	$34.55	$34.50
Purchase #5	$6.83	7.315%	$7.3296	$7.33	$7.35	$7.30
Purchase #6	$231.92	5.751%	$245.2577	$245.26	$245.25	$245.30
Purchase #7	$173.86	12.752%	$196.0306	$196.03	$196.05	$196.00
7 purchase totals =	$820.78		$882.6372	$882.64	$882.70	$882.60