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	$177.31	10.252%	$195.4878	$195.49	$195.50	$195.50
Purchase #2	$90.76	9.507%	$99.3886	$99.39	$99.40	$99.40
Purchase #3	$39.50	13.544%	$44.8499	$44.85	$44.85	$44.80
Purchase #4	$171.61	7.793%	$184.9836	$184.98	$185.00	$185.00
Purchase #5	$38.59	11.691%	$43.1016	$43.10	$43.10	$43.10
Purchase #6	$49.86	9.688%	$54.6904	$54.69	$54.70	$54.70
Purchase #7	$209.73	11.756%	$234.3859	$234.39	$234.40	$234.40
7 purchase totals =	$777.36		$856.8878	$856.89	$856.95	$856.90