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	$247.98	4.410%	$258.9159	$258.92	$258.90	$258.90
Purchase #2	$73.83	5.762%	$78.0841	$78.08	$78.10	$78.10
Purchase #3	$31.46	11.372%	$35.0376	$35.04	$35.05	$35.00
Purchase #4	$59.62	4.236%	$62.1455	$62.15	$62.15	$62.10
Purchase #5	$42.48	13.188%	$48.0823	$48.08	$48.10	$48.10
Purchase #6	$170.82	11.542%	$190.536	$190.54	$190.55	$190.50
Purchase #7	$207.64	6.842%	$221.8467	$221.85	$221.85	$221.80
7 purchase totals =	$833.83		$894.6481	$894.66	$894.70	$894.50