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	$73.39	11.853%	$82.0889	$82.09	$82.10	$82.10
Purchase #2	$146.39	3.683%	$151.7815	$151.78	$151.80	$151.80
Purchase #3	$173.61	13.346%	$196.78	$196.78	$196.80	$196.80
Purchase #4	$43.79	3.570%	$45.3533	$45.35	$45.35	$45.40
Purchase #5	$41.40	8.600%	$44.9604	$44.96	$44.95	$45.00
Purchase #6	$147.93	12.868%	$166.9656	$166.97	$166.95	$167.00
Purchase #7	$196.63	9.632%	$215.5694	$215.57	$215.55	$215.60
7 purchase totals =	$823.14		$903.4991	$903.50	$903.50	$903.70