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	$141.29	6.266%	$150.1432	$150.14	$150.15	$150.10
Purchase #2	$133.35	5.836%	$141.1323	$141.13	$141.15	$141.10
Purchase #3	$163.26	13.518%	$185.3295	$185.33	$185.35	$185.30
Purchase #4	$229.69	6.672%	$245.0149	$245.01	$245.00	$245.00
Purchase #5	$155.43	3.495%	$160.8623	$160.86	$160.85	$160.90
Purchase #6	$167.78	6.569%	$178.8015	$178.80	$178.80	$178.80
Purchase #7	$66.85	7.357%	$71.7682	$71.77	$71.75	$71.80
7 purchase totals =	$1,057.65		$1,133.0519	$1,133.04	$1,133.05	$1,133.00