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	$146.44	4.202%	$152.5934	$152.59	$152.60	$152.60
Purchase #2	$81.71	9.254%	$89.2714	$89.27	$89.25	$89.30
Purchase #3	$196.74	9.561%	$215.5503	$215.55	$215.55	$215.60
Purchase #4	$219.70	8.683%	$238.7766	$238.78	$238.80	$238.80
Purchase #5	$208.76	4.184%	$217.4945	$217.49	$217.50	$217.50
Purchase #6	$49.33	7.241%	$52.902	$52.90	$52.90	$52.90
Purchase #7	$239.97	9.739%	$263.3407	$263.34	$263.35	$263.30
7 purchase totals =	$1,142.65		$1,229.9289	$1,229.92	$1,229.95	$1,230.00