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	$101.82	7.752%	$109.7131	$109.71	$109.70	$109.70
Purchase #2	$100.79	7.724%	$108.575	$108.58	$108.60	$108.60
Purchase #3	$93.78	12.280%	$105.2962	$105.30	$105.30	$105.30
Purchase #4	$35.26	6.457%	$37.5367	$37.54	$37.55	$37.50
Purchase #5	$180.79	8.675%	$196.4735	$196.47	$196.45	$196.50
Purchase #6	$112.97	6.179%	$119.9504	$119.95	$119.95	$120.00
Purchase #7	$161.60	6.376%	$171.9036	$171.90	$171.90	$171.90
7 purchase totals =	$787.01		$849.4485	$849.45	$849.45	$849.50