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	$132.56	12.740%	$149.4481	$149.45	$149.45	$149.40
Purchase #2	$19.72	5.802%	$20.8642	$20.86	$20.85	$20.90
Purchase #3	$78.88	9.192%	$86.1306	$86.13	$86.15	$86.10
Purchase #4	$83.28	4.579%	$87.0934	$87.09	$87.10	$87.10
Purchase #5	$59.98	4.459%	$62.6545	$62.65	$62.65	$62.70
Purchase #6	$140.32	11.179%	$156.0064	$156.01	$156.00	$156.00
Purchase #7	$98.63	5.153%	$103.7124	$103.71	$103.70	$103.70
7 purchase totals =	$613.37		$665.9096	$665.90	$665.90	$665.90