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	$102.35	8.698%	$111.2524	$111.25	$111.25	$111.30
Purchase #2	$5.72	8.801%	$6.2234	$6.22	$6.20	$6.20
Purchase #3	$35.77	13.151%	$40.4741	$40.47	$40.45	$40.50
Purchase #4	$59.57	6.163%	$63.2413	$63.24	$63.25	$63.20
Purchase #5	$28.95	11.401%	$32.2506	$32.25	$32.25	$32.30
Purchase #6	$72.29	11.187%	$80.3771	$80.38	$80.40	$80.40
Purchase #7	$248.89	9.713%	$273.0647	$273.06	$273.05	$273.10
7 purchase totals =	$553.54		$606.8836	$606.87	$606.85	$607.00