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	$81.56	13.565%	$92.6236	$92.62	$92.60	$92.60
Purchase #2	$77.86	7.126%	$83.4083	$83.41	$83.40	$83.40
Purchase #3	$168.32	9.248%	$183.8862	$183.89	$183.90	$183.90
Purchase #4	$127.29	12.471%	$143.1643	$143.16	$143.15	$143.20
Purchase #5	$80.71	8.526%	$87.5913	$87.59	$87.60	$87.60
Purchase #6	$60.36	6.357%	$64.1971	$64.20	$64.20	$64.20
Purchase #7	$69.69	3.174%	$71.902	$71.90	$71.90	$71.90
7 purchase totals =	$665.79		$726.7728	$726.77	$726.75	$726.80