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	$158.88	12.669%	$179.0085	$179.01	$179.00	$179.00
Purchase #2	$41.59	9.423%	$45.509	$45.51	$45.50	$45.50
Purchase #3	$184.71	9.164%	$201.6368	$201.64	$201.65	$201.60
Purchase #4	$161.83	3.508%	$167.507	$167.51	$167.50	$167.50
Purchase #5	$14.63	8.236%	$15.8349	$15.83	$15.85	$15.80
Purchase #6	$150.88	9.557%	$165.2996	$165.30	$165.30	$165.30
Purchase #7	$168.54	6.614%	$179.6872	$179.69	$179.70	$179.70
7 purchase totals =	$881.06		$954.4830	$954.49	$954.50	$954.40