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	$58.55	3.807%	$60.779	$60.78	$60.80	$60.80
Purchase #2	$163.68	11.547%	$182.5801	$182.58	$182.60	$182.60
Purchase #3	$169.45	7.478%	$182.1215	$182.12	$182.10	$182.10
Purchase #4	$89.67	8.796%	$97.5574	$97.56	$97.55	$97.60
Purchase #5	$61.87	9.668%	$67.8516	$67.85	$67.85	$67.90
Purchase #6	$158.87	4.153%	$165.4679	$165.47	$165.45	$165.50
Purchase #7	$178.50	4.504%	$186.5396	$186.54	$186.55	$186.50
7 purchase totals =	$880.59		$942.8971	$942.90	$942.90	$943.00