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	$120.38	9.628%	$131.9702	$131.97	$131.95	$132.00
Purchase #2	$131.32	11.847%	$146.8775	$146.88	$146.90	$146.90
Purchase #3	$189.28	4.624%	$198.0323	$198.03	$198.05	$198.00
Purchase #4	$242.82	11.144%	$269.8799	$269.88	$269.90	$269.90
Purchase #5	$207.50	10.317%	$228.9078	$228.91	$228.90	$228.90
Purchase #6	$215.43	6.233%	$228.8578	$228.86	$228.85	$228.90
Purchase #7	$201.75	8.516%	$218.931	$218.93	$218.95	$218.90
7 purchase totals =	$1,308.48		$1,423.4565	$1,423.46	$1,423.50	$1,423.50