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	$222.81	10.313%	$245.7884	$245.79	$245.80	$245.80
Purchase #2	$148.81	12.737%	$167.7639	$167.76	$167.75	$167.80
Purchase #3	$30.51	5.353%	$32.1432	$32.14	$32.15	$32.10
Purchase #4	$115.51	11.533%	$128.8318	$128.83	$128.85	$128.80
Purchase #5	$20.89	8.169%	$22.5965	$22.60	$22.60	$22.60
Purchase #6	$176.70	3.141%	$182.2501	$182.25	$182.25	$182.30
Purchase #7	$42.90	10.575%	$47.4367	$47.44	$47.45	$47.40
7 purchase totals =	$758.13		$826.8106	$826.81	$826.85	$826.80