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	$165.83	4.224%	$172.8347	$172.83	$172.85	$172.80
Purchase #2	$184.89	6.245%	$196.4364	$196.44	$196.45	$196.40
Purchase #3	$31.43	12.423%	$35.3345	$35.33	$35.35	$35.30
Purchase #4	$18.88	3.167%	$19.4779	$19.48	$19.50	$19.50
Purchase #5	$95.48	9.167%	$104.2327	$104.23	$104.25	$104.20
Purchase #6	$170.89	11.422%	$190.4091	$190.41	$190.40	$190.40
Purchase #7	$41.52	4.520%	$43.3967	$43.40	$43.40	$43.40
7 purchase totals =	$708.92		$762.1220	$762.12	$762.20	$762.00