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	$223.98	11.120%	$248.8866	$248.89	$248.90	$248.90
Purchase #2	$13.52	12.812%	$15.2522	$15.25	$15.25	$15.30
Purchase #3	$249.86	8.258%	$270.4934	$270.49	$270.50	$270.50
Purchase #4	$189.36	3.717%	$196.3985	$196.40	$196.40	$196.40
Purchase #5	$13.89	8.190%	$15.0276	$15.03	$15.05	$15.00
Purchase #6	$158.52	10.214%	$174.7112	$174.71	$174.70	$174.70
Purchase #7	$43.82	4.857%	$45.9483	$45.95	$45.95	$45.90
7 purchase totals =	$892.95		$966.7178	$966.72	$966.75	$966.70