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	$41.48	4.710%	$43.4337	$43.43	$43.45	$43.40
Purchase #2	$150.89	13.659%	$171.5001	$171.50	$171.50	$171.50
Purchase #3	$91.46	6.335%	$97.254	$97.25	$97.25	$97.30
Purchase #4	$75.61	4.710%	$79.1712	$79.17	$79.15	$79.20
Purchase #5	$45.76	12.855%	$51.6424	$51.64	$51.65	$51.60
Purchase #6	$39.35	10.716%	$43.5667	$43.57	$43.55	$43.60
Purchase #7	$209.55	3.395%	$216.6642	$216.66	$216.65	$216.70
7 purchase totals =	$654.10		$703.2323	$703.22	$703.20	$703.30