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	$246.71	3.113%	$254.3901	$254.39	$254.40	$254.40
Purchase #2	$93.43	7.497%	$100.4344	$100.43	$100.45	$100.40
Purchase #3	$155.49	5.647%	$164.2705	$164.27	$164.25	$164.30
Purchase #4	$46.52	10.270%	$51.2976	$51.30	$51.30	$51.30
Purchase #5	$193.57	10.197%	$213.3083	$213.31	$213.30	$213.30
Purchase #6	$95.51	8.197%	$103.339	$103.34	$103.35	$103.30
Purchase #7	$44.98	7.486%	$48.3472	$48.35	$48.35	$48.30
7 purchase totals =	$876.21		$935.3871	$935.39	$935.40	$935.30