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	$217.50	11.693%	$242.9323	$242.93	$242.95	$242.90
Purchase #2	$250.65	3.467%	$259.34	$259.34	$259.35	$259.30
Purchase #3	$81.96	5.264%	$86.2744	$86.27	$86.25	$86.30
Purchase #4	$152.66	10.653%	$168.9229	$168.92	$168.90	$168.90
Purchase #5	$92.96	9.242%	$101.5514	$101.55	$101.55	$101.60
Purchase #6	$217.96	3.211%	$224.9587	$224.96	$224.95	$225.00
Purchase #7	$131.81	4.250%	$137.4119	$137.41	$137.40	$137.40
7 purchase totals =	$1,145.50		$1,221.3916	$1,221.38	$1,221.35	$1,221.40