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	$155.89	4.311%	$162.6104	$162.61	$162.60	$162.60
Purchase #2	$118.41	11.310%	$131.8022	$131.80	$131.80	$131.80
Purchase #3	$163.61	6.733%	$174.6259	$174.63	$174.65	$174.60
Purchase #4	$179.56	6.638%	$191.4792	$191.48	$191.50	$191.50
Purchase #5	$55.73	7.721%	$60.0329	$60.03	$60.05	$60.00
Purchase #6	$22.31	9.871%	$24.5122	$24.51	$24.50	$24.50
Purchase #7	$239.60	8.329%	$259.5563	$259.56	$259.55	$259.60
7 purchase totals =	$935.11		$1,004.6191	$1,004.62	$1,004.65	$1,004.60