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	$37.70	7.425%	$40.4992	$40.50	$40.50	$40.50
Purchase #2	$184.87	3.609%	$191.542	$191.54	$191.55	$191.50
Purchase #3	$249.58	6.173%	$264.9866	$264.99	$265.00	$265.00
Purchase #4	$82.79	9.344%	$90.5259	$90.53	$90.55	$90.50
Purchase #5	$147.36	6.271%	$156.6009	$156.60	$156.60	$156.60
Purchase #6	$241.33	11.257%	$268.4965	$268.50	$268.50	$268.50
Purchase #7	$8.69	11.863%	$9.7209	$9.72	$9.70	$9.70
7 purchase totals =	$952.32		$1,022.3720	$1,022.38	$1,022.40	$1,022.30