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	$226.87	8.601%	$246.3831	$246.38	$246.40	$246.40
Purchase #2	$215.70	11.418%	$240.3286	$240.33	$240.35	$240.30
Purchase #3	$117.37	8.553%	$127.4087	$127.41	$127.40	$127.40
Purchase #4	$194.37	3.106%	$200.4071	$200.41	$200.40	$200.40
Purchase #5	$6.71	7.873%	$7.2383	$7.24	$7.25	$7.20
Purchase #6	$40.92	10.687%	$45.2931	$45.29	$45.30	$45.30
Purchase #7	$127.82	4.719%	$133.8518	$133.85	$133.85	$133.90
7 purchase totals =	$929.76		$1,000.9107	$1,000.91	$1,000.95	$1,000.90