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	$226.71	4.551%	$237.0276	$237.03	$237.05	$237.00
Purchase #2	$238.58	3.489%	$246.9041	$246.90	$246.90	$246.90
Purchase #3	$188.97	4.140%	$196.7934	$196.79	$196.80	$196.80
Purchase #4	$164.94	4.184%	$171.8411	$171.84	$171.85	$171.80
Purchase #5	$63.42	13.574%	$72.0286	$72.03	$72.05	$72.00
Purchase #6	$61.73	8.344%	$66.8808	$66.88	$66.90	$66.90
Purchase #7	$59.94	11.164%	$66.6317	$66.63	$66.65	$66.60
7 purchase totals =	$1,004.29		$1,058.1073	$1,058.10	$1,058.20	$1,058.00