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	$140.47	10.473%	$155.1814	$155.18	$155.20	$155.20
Purchase #2	$31.40	13.846%	$35.7476	$35.75	$35.75	$35.70
Purchase #3	$101.27	12.263%	$113.6887	$113.69	$113.70	$113.70
Purchase #4	$31.61	6.252%	$33.5863	$33.59	$33.60	$33.60
Purchase #5	$88.83	11.242%	$98.8163	$98.82	$98.80	$98.80
Purchase #6	$140.91	12.632%	$158.7098	$158.71	$158.70	$158.70
Purchase #7	$158.76	4.219%	$165.4581	$165.46	$165.45	$165.50
7 purchase totals =	$693.25		$761.1882	$761.20	$761.20	$761.20