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	$89.37	3.665%	$92.6454	$92.65	$92.65	$92.60
Purchase #2	$151.38	11.829%	$169.2867	$169.29	$169.30	$169.30
Purchase #3	$161.42	13.335%	$182.9454	$182.95	$182.95	$182.90
Purchase #4	$234.96	10.605%	$259.8775	$259.88	$259.90	$259.90
Purchase #5	$189.57	3.627%	$196.4457	$196.45	$196.45	$196.40
Purchase #6	$200.97	9.662%	$220.3877	$220.39	$220.40	$220.40
Purchase #7	$133.91	10.505%	$147.9772	$147.98	$148.00	$148.00
7 purchase totals =	$1,161.58		$1,269.5656	$1,269.59	$1,269.65	$1,269.50