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	$146.84	13.789%	$167.0878	$167.09	$167.10	$167.10
Purchase #2	$115.46	3.728%	$119.7643	$119.76	$119.75	$119.80
Purchase #3	$94.56	6.744%	$100.9371	$100.94	$100.95	$100.90
Purchase #4	$125.60	13.752%	$142.8725	$142.87	$142.85	$142.90
Purchase #5	$128.31	6.872%	$137.1275	$137.13	$137.15	$137.10
Purchase #6	$134.98	9.870%	$148.3025	$148.30	$148.30	$148.30
Purchase #7	$147.62	5.268%	$155.3966	$155.40	$155.40	$155.40
7 purchase totals =	$893.37		$971.4883	$971.49	$971.50	$971.50