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	$101.61	12.746%	$114.5612	$114.56	$114.55	$114.60
Purchase #2	$194.61	3.165%	$200.7694	$200.77	$200.75	$200.80
Purchase #3	$242.41	7.515%	$260.6271	$260.63	$260.65	$260.60
Purchase #4	$54.55	13.345%	$61.8297	$61.83	$61.85	$61.80
Purchase #5	$140.44	3.108%	$144.8049	$144.80	$144.80	$144.80
Purchase #6	$19.33	11.477%	$21.5485	$21.55	$21.55	$21.50
Purchase #7	$51.64	6.519%	$55.0064	$55.01	$55.00	$55.00
7 purchase totals =	$804.59		$859.1472	$859.15	$859.15	$859.10