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	$216.31	13.486%	$245.4816	$245.48	$245.50	$245.50
Purchase #2	$127.29	11.556%	$141.9996	$142.00	$142.00	$142.00
Purchase #3	$221.79	13.542%	$251.8248	$251.82	$251.80	$251.80
Purchase #4	$148.33	13.627%	$168.5429	$168.54	$168.55	$168.50
Purchase #5	$42.67	6.171%	$45.3032	$45.30	$45.30	$45.30
Purchase #6	$93.31	12.387%	$104.8683	$104.87	$104.85	$104.90
Purchase #7	$150.44	9.639%	$164.9409	$164.94	$164.95	$164.90
7 purchase totals =	$1,000.14		$1,122.9613	$1,122.95	$1,122.95	$1,122.90