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	$224.61	11.474%	$250.3818	$250.38	$250.40	$250.40
Purchase #2	$59.97	3.299%	$61.9484	$61.95	$61.95	$61.90
Purchase #3	$144.97	8.712%	$157.5998	$157.60	$157.60	$157.60
Purchase #4	$112.80	9.597%	$123.6254	$123.63	$123.65	$123.60
Purchase #5	$184.85	3.530%	$191.3752	$191.38	$191.40	$191.40
Purchase #6	$90.46	8.861%	$98.4757	$98.48	$98.50	$98.50
Purchase #7	$50.59	4.570%	$52.902	$52.90	$52.90	$52.90
7 purchase totals =	$868.25		$936.3083	$936.32	$936.40	$936.30