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	$31.26	5.336%	$32.928	$32.93	$32.95	$32.90
Purchase #2	$198.70	9.349%	$217.2765	$217.28	$217.30	$217.30
Purchase #3	$188.36	7.838%	$203.1237	$203.12	$203.10	$203.10
Purchase #4	$84.29	5.655%	$89.0566	$89.06	$89.05	$89.10
Purchase #5	$164.71	9.175%	$179.8221	$179.82	$179.80	$179.80
Purchase #6	$64.37	5.481%	$67.8981	$67.90	$67.90	$67.90
Purchase #7	$160.41	3.794%	$166.496	$166.50	$166.50	$166.50
7 purchase totals =	$892.10		$956.6010	$956.61	$956.60	$956.60