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	$131.96	6.112%	$140.0254	$140.03	$140.05	$140.00
Purchase #2	$99.98	12.474%	$112.4515	$112.45	$112.45	$112.50
Purchase #3	$47.84	13.732%	$54.4094	$54.41	$54.40	$54.40
Purchase #4	$35.72	10.588%	$39.502	$39.50	$39.50	$39.50
Purchase #5	$151.63	9.413%	$165.9029	$165.90	$165.90	$165.90
Purchase #6	$189.31	8.518%	$205.4354	$205.44	$205.45	$205.40
Purchase #7	$200.25	8.840%	$217.9521	$217.95	$217.95	$218.00
7 purchase totals =	$856.69		$935.6787	$935.68	$935.70	$935.70