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	$148.80	7.217%	$159.5389	$159.54	$159.55	$159.50
Purchase #2	$232.94	9.264%	$254.5196	$254.52	$254.50	$254.50
Purchase #3	$204.93	5.326%	$215.8446	$215.84	$215.85	$215.80
Purchase #4	$44.65	4.471%	$46.6463	$46.65	$46.65	$46.60
Purchase #5	$179.80	11.255%	$200.0365	$200.04	$200.05	$200.00
Purchase #6	$42.81	10.796%	$47.4318	$47.43	$47.45	$47.40
Purchase #7	$69.54	4.800%	$72.8779	$72.88	$72.90	$72.90
7 purchase totals =	$923.47		$996.8956	$996.90	$996.95	$996.70