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	$57.55	4.507%	$60.1438	$60.14	$60.15	$60.10
Purchase #2	$78.55	13.511%	$89.1629	$89.16	$89.15	$89.20
Purchase #3	$113.70	10.758%	$125.9318	$125.93	$125.95	$125.90
Purchase #4	$172.64	11.402%	$192.3244	$192.32	$192.30	$192.30
Purchase #5	$134.46	4.697%	$140.7756	$140.78	$140.80	$140.80
Purchase #6	$175.58	6.469%	$186.9383	$186.94	$186.95	$186.90
Purchase #7	$199.99	4.250%	$208.4896	$208.49	$208.50	$208.50
7 purchase totals =	$932.47		$1,003.7664	$1,003.76	$1,003.80	$1,003.70