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	$178.29	12.237%	$200.1073	$200.11	$200.10	$200.10
Purchase #2	$192.54	5.654%	$203.4262	$203.43	$203.45	$203.40
Purchase #3	$41.58	13.133%	$47.0407	$47.04	$47.05	$47.00
Purchase #4	$49.83	4.622%	$52.1331	$52.13	$52.15	$52.10
Purchase #5	$225.61	5.645%	$238.3457	$238.35	$238.35	$238.30
Purchase #6	$132.80	9.575%	$145.5156	$145.52	$145.50	$145.50
Purchase #7	$145.73	12.765%	$164.3324	$164.33	$164.35	$164.30
7 purchase totals =	$966.38		$1,050.9010	$1,050.91	$1,050.95	$1,050.70