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	$111.73	4.506%	$116.7646	$116.76	$116.75	$116.80
Purchase #2	$154.79	7.774%	$166.8234	$166.82	$166.80	$166.80
Purchase #3	$77.54	9.756%	$85.1048	$85.10	$85.10	$85.10
Purchase #4	$232.61	5.799%	$246.0991	$246.10	$246.10	$246.10
Purchase #5	$109.29	13.724%	$124.289	$124.29	$124.30	$124.30
Purchase #6	$128.51	13.209%	$145.4849	$145.48	$145.50	$145.50
Purchase #7	$35.31	7.867%	$38.0878	$38.09	$38.10	$38.10
7 purchase totals =	$849.78		$922.6536	$922.64	$922.65	$922.70