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	$71.73	9.604%	$78.6189	$78.62	$78.60	$78.60
Purchase #2	$222.52	11.618%	$248.3724	$248.37	$248.35	$248.40
Purchase #3	$186.63	5.396%	$196.7006	$196.70	$196.70	$196.70
Purchase #4	$246.51	11.846%	$275.7116	$275.71	$275.70	$275.70
Purchase #5	$31.63	9.200%	$34.54	$34.54	$34.55	$34.50
Purchase #6	$233.46	7.196%	$250.2598	$250.26	$250.25	$250.30
Purchase #7	$114.76	5.810%	$121.4276	$121.43	$121.45	$121.40
7 purchase totals =	$1,107.24		$1,205.6309	$1,205.63	$1,205.60	$1,205.60