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	$84.47	13.133%	$95.5634	$95.56	$95.55	$95.60
Purchase #2	$56.40	6.528%	$60.0818	$60.08	$60.10	$60.10
Purchase #3	$181.81	10.264%	$200.471	$200.47	$200.45	$200.50
Purchase #4	$98.32	6.191%	$104.407	$104.41	$104.40	$104.40
Purchase #5	$59.37	11.358%	$66.1132	$66.11	$66.10	$66.10
Purchase #6	$213.71	13.462%	$242.4796	$242.48	$242.50	$242.50
Purchase #7	$122.70	7.807%	$132.2792	$132.28	$132.30	$132.30
7 purchase totals =	$816.78		$901.3952	$901.39	$901.40	$901.50