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	$153.37	11.306%	$170.71	$170.71	$170.70	$170.70
Purchase #2	$119.31	6.223%	$126.7347	$126.73	$126.75	$126.70
Purchase #3	$17.56	4.249%	$18.3061	$18.31	$18.30	$18.30
Purchase #4	$133.86	6.260%	$142.2396	$142.24	$142.25	$142.20
Purchase #5	$71.60	10.232%	$78.9261	$78.93	$78.95	$78.90
Purchase #6	$165.91	9.871%	$182.287	$182.29	$182.30	$182.30
Purchase #7	$12.77	6.639%	$13.6178	$13.62	$13.60	$13.60
7 purchase totals =	$674.38		$732.8213	$732.83	$732.85	$732.70