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	$42.49	11.380%	$47.3254	$47.33	$47.35	$47.30
Purchase #2	$170.93	11.678%	$190.8912	$190.89	$190.90	$190.90
Purchase #3	$41.75	6.593%	$44.5026	$44.50	$44.50	$44.50
Purchase #4	$35.44	6.779%	$37.8425	$37.84	$37.85	$37.80
Purchase #5	$53.90	13.848%	$61.3641	$61.36	$61.35	$61.40
Purchase #6	$69.41	10.195%	$76.4863	$76.49	$76.50	$76.50
Purchase #7	$196.89	10.545%	$217.6521	$217.65	$217.65	$217.70
7 purchase totals =	$610.81		$676.0642	$676.06	$676.10	$676.10