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	$206.84	4.314%	$215.7631	$215.76	$215.75	$215.80
Purchase #2	$192.48	4.364%	$200.8798	$200.88	$200.90	$200.90
Purchase #3	$200.61	5.869%	$212.3838	$212.38	$212.40	$212.40
Purchase #4	$92.86	4.307%	$96.8595	$96.86	$96.85	$96.90
Purchase #5	$77.36	6.641%	$82.4975	$82.50	$82.50	$82.50
Purchase #6	$5.60	4.261%	$5.8386	$5.84	$5.85	$5.80
Purchase #7	$74.88	5.131%	$78.7221	$78.72	$78.70	$78.70
7 purchase totals =	$850.63		$892.9444	$892.94	$892.95	$893.00