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	$191.59	4.650%	$200.4989	$200.50	$200.50	$200.50
Purchase #2	$152.43	10.380%	$168.2522	$168.25	$168.25	$168.30
Purchase #3	$96.32	13.135%	$108.9716	$108.97	$108.95	$109.00
Purchase #4	$219.37	10.297%	$241.9585	$241.96	$241.95	$242.00
Purchase #5	$201.90	10.227%	$222.5483	$222.55	$222.55	$222.50
Purchase #6	$150.80	5.359%	$158.8814	$158.88	$158.90	$158.90
Purchase #7	$224.87	10.475%	$248.4251	$248.43	$248.45	$248.40
7 purchase totals =	$1,237.28		$1,349.5360	$1,349.54	$1,349.55	$1,349.60