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	$131.44	7.381%	$141.1416	$141.14	$141.15	$141.10
Purchase #2	$237.28	12.853%	$267.7776	$267.78	$267.80	$267.80
Purchase #3	$226.25	6.177%	$240.2255	$240.23	$240.25	$240.20
Purchase #4	$82.90	4.349%	$86.5053	$86.51	$86.50	$86.50
Purchase #5	$77.88	10.581%	$86.1205	$86.12	$86.10	$86.10
Purchase #6	$36.30	12.426%	$40.8106	$40.81	$40.80	$40.80
Purchase #7	$130.39	9.210%	$142.3989	$142.40	$142.40	$142.40
7 purchase totals =	$922.44		$1,004.9800	$1,004.99	$1,005.00	$1,004.90