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	$144.45	12.742%	$162.8558	$162.86	$162.85	$162.90
Purchase #2	$137.58	3.870%	$142.9043	$142.90	$142.90	$142.90
Purchase #3	$168.47	10.780%	$186.6311	$186.63	$186.65	$186.60
Purchase #4	$166.42	5.727%	$175.9509	$175.95	$175.95	$176.00
Purchase #5	$91.86	7.591%	$98.8331	$98.83	$98.85	$98.80
Purchase #6	$180.58	3.521%	$186.9382	$186.94	$186.95	$186.90
Purchase #7	$42.62	12.705%	$48.0349	$48.03	$48.05	$48.00
7 purchase totals =	$931.98		$1,002.1483	$1,002.14	$1,002.20	$1,002.10