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	$145.61	12.554%	$163.8899	$163.89	$163.90	$163.90
Purchase #2	$78.76	8.596%	$85.5302	$85.53	$85.55	$85.50
Purchase #3	$179.32	4.358%	$187.1348	$187.13	$187.15	$187.10
Purchase #4	$249.35	12.315%	$280.0575	$280.06	$280.05	$280.10
Purchase #5	$70.61	11.647%	$78.8339	$78.83	$78.85	$78.80
Purchase #6	$193.34	12.326%	$217.1711	$217.17	$217.15	$217.20
Purchase #7	$242.43	3.594%	$251.1429	$251.14	$251.15	$251.10
7 purchase totals =	$1,159.42		$1,263.7603	$1,263.75	$1,263.80	$1,263.70