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	$71.77	9.756%	$78.7719	$78.77	$78.75	$78.80
Purchase #2	$132.54	11.576%	$147.8828	$147.88	$147.90	$147.90
Purchase #3	$224.99	4.218%	$234.4801	$234.48	$234.50	$234.50
Purchase #4	$57.67	8.375%	$62.4999	$62.50	$62.50	$62.50
Purchase #5	$192.59	10.329%	$212.4826	$212.48	$212.50	$212.50
Purchase #6	$59.87	9.319%	$65.4493	$65.45	$65.45	$65.40
Purchase #7	$195.76	12.706%	$220.6333	$220.63	$220.65	$220.60
7 purchase totals =	$935.19		$1,022.1999	$1,022.19	$1,022.25	$1,022.20