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	$239.30	7.745%	$257.8338	$257.83	$257.85	$257.80
Purchase #2	$45.84	5.568%	$48.3924	$48.39	$48.40	$48.40
Purchase #3	$246.49	6.342%	$262.1224	$262.12	$262.10	$262.10
Purchase #4	$183.50	13.262%	$207.8358	$207.84	$207.85	$207.80
Purchase #5	$67.98	3.427%	$70.3097	$70.31	$70.30	$70.30
Purchase #6	$89.80	6.828%	$95.9315	$95.93	$95.95	$95.90
Purchase #7	$87.41	3.500%	$90.4694	$90.47	$90.45	$90.50
7 purchase totals =	$960.32		$1,032.8950	$1,032.89	$1,032.90	$1,032.80