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	$154.61	9.659%	$169.5438	$169.54	$169.55	$169.50
Purchase #2	$64.99	12.202%	$72.9201	$72.92	$72.90	$72.90
Purchase #3	$185.33	8.342%	$200.7902	$200.79	$200.80	$200.80
Purchase #4	$47.34	10.144%	$52.1422	$52.14	$52.15	$52.10
Purchase #5	$233.66	9.516%	$255.8951	$255.90	$255.90	$255.90
Purchase #6	$20.34	12.844%	$22.9525	$22.95	$22.95	$23.00
Purchase #7	$141.57	12.477%	$159.2337	$159.23	$159.25	$159.20
7 purchase totals =	$847.84		$933.4776	$933.47	$933.50	$933.40