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	$59.56	4.126%	$62.0174	$62.02	$62.00	$62.00
Purchase #2	$18.32	5.375%	$19.3047	$19.30	$19.30	$19.30
Purchase #3	$171.57	10.344%	$189.3172	$189.32	$189.30	$189.30
Purchase #4	$12.75	8.861%	$13.8798	$13.88	$13.90	$13.90
Purchase #5	$18.88	13.868%	$21.4983	$21.50	$21.50	$21.50
Purchase #6	$82.71	9.572%	$90.627	$90.63	$90.65	$90.60
Purchase #7	$210.85	13.869%	$240.0928	$240.09	$240.10	$240.10
7 purchase totals =	$574.64		$636.7372	$636.74	$636.75	$636.70