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	$242.80	7.673%	$261.43	$261.43	$261.45	$261.40
Purchase #2	$41.66	3.725%	$43.2118	$43.21	$43.20	$43.20
Purchase #3	$156.74	9.411%	$171.4908	$171.49	$171.50	$171.50
Purchase #4	$167.76	13.285%	$190.0469	$190.05	$190.05	$190.00
Purchase #5	$203.88	13.465%	$231.3324	$231.33	$231.35	$231.30
Purchase #6	$105.60	4.628%	$110.4872	$110.49	$110.50	$110.50
Purchase #7	$115.77	13.514%	$131.4152	$131.42	$131.40	$131.40
7 purchase totals =	$1,034.21		$1,139.4143	$1,139.42	$1,139.45	$1,139.30