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	$222.93	3.848%	$231.5083	$231.51	$231.50	$231.50
Purchase #2	$209.73	10.121%	$230.9568	$230.96	$230.95	$231.00
Purchase #3	$9.56	12.807%	$10.7843	$10.78	$10.80	$10.80
Purchase #4	$247.47	10.671%	$273.8775	$273.88	$273.90	$273.90
Purchase #5	$250.87	10.818%	$278.0091	$278.01	$278.00	$278.00
Purchase #6	$68.81	7.386%	$73.8923	$73.89	$73.90	$73.90
Purchase #7	$146.58	12.474%	$164.8644	$164.86	$164.85	$164.90
7 purchase totals =	$1,155.95		$1,263.8927	$1,263.89	$1,263.90	$1,264.00