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	$45.65	4.177%	$47.5568	$47.56	$47.55	$47.60
Purchase #2	$161.79	12.651%	$182.2581	$182.26	$182.25	$182.30
Purchase #3	$133.98	7.325%	$143.794	$143.79	$143.80	$143.80
Purchase #4	$57.89	13.833%	$65.8979	$65.90	$65.90	$65.90
Purchase #5	$68.71	13.497%	$77.9838	$77.98	$78.00	$78.00
Purchase #6	$67.55	9.140%	$73.7241	$73.72	$73.70	$73.70
Purchase #7	$210.43	9.118%	$229.617	$229.62	$229.60	$229.60
7 purchase totals =	$746.00		$820.8317	$820.83	$820.80	$820.90