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	$59.55	4.652%	$62.3203	$62.32	$62.30	$62.30
Purchase #2	$133.42	7.212%	$143.0423	$143.04	$143.05	$143.00
Purchase #3	$228.48	11.798%	$255.4361	$255.44	$255.45	$255.40
Purchase #4	$30.76	9.718%	$33.7493	$33.75	$33.75	$33.70
Purchase #5	$20.76	3.369%	$21.4594	$21.46	$21.45	$21.50
Purchase #6	$140.89	4.633%	$147.4174	$147.42	$147.40	$147.40
Purchase #7	$98.39	4.163%	$102.486	$102.49	$102.50	$102.50
7 purchase totals =	$712.25		$765.9108	$765.92	$765.90	$765.80