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	$126.87	11.749%	$141.776	$141.78	$141.80	$141.80
Purchase #2	$82.45	13.126%	$93.2724	$93.27	$93.25	$93.30
Purchase #3	$109.36	8.418%	$118.5659	$118.57	$118.55	$118.60
Purchase #4	$152.97	7.640%	$164.6569	$164.66	$164.65	$164.70
Purchase #5	$197.57	13.637%	$224.5126	$224.51	$224.50	$224.50
Purchase #6	$119.43	3.150%	$123.192	$123.19	$123.20	$123.20
Purchase #7	$58.96	11.730%	$65.876	$65.88	$65.90	$65.90
7 purchase totals =	$847.61		$931.8518	$931.86	$931.85	$932.00