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	$217.39	7.688%	$234.1029	$234.10	$234.10	$234.10
Purchase #2	$174.53	7.587%	$187.7716	$187.77	$187.75	$187.80
Purchase #3	$71.40	10.324%	$78.7713	$78.77	$78.75	$78.80
Purchase #4	$52.77	6.216%	$56.0502	$56.05	$56.05	$56.10
Purchase #5	$133.57	7.778%	$143.9591	$143.96	$143.95	$144.00
Purchase #6	$52.73	5.829%	$55.8036	$55.80	$55.80	$55.80
Purchase #7	$164.86	6.688%	$175.8858	$175.89	$175.90	$175.90
7 purchase totals =	$867.25		$932.3445	$932.34	$932.30	$932.50