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	$60.73	3.856%	$63.0717	$63.07	$63.05	$63.10
Purchase #2	$238.94	13.201%	$270.4825	$270.48	$270.50	$270.50
Purchase #3	$37.76	7.499%	$40.5916	$40.59	$40.60	$40.60
Purchase #4	$95.50	7.331%	$102.5011	$102.50	$102.50	$102.50
Purchase #5	$178.91	8.762%	$194.5861	$194.59	$194.60	$194.60
Purchase #6	$184.93	6.292%	$196.5658	$196.57	$196.55	$196.60
Purchase #7	$48.83	11.846%	$54.6144	$54.61	$54.60	$54.60
7 purchase totals =	$845.60		$922.4132	$922.41	$922.40	$922.50