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	$241.68	13.407%	$274.082	$274.08	$274.10	$274.10
Purchase #2	$227.41	3.525%	$235.4262	$235.43	$235.45	$235.40
Purchase #3	$33.47	7.271%	$35.9036	$35.90	$35.90	$35.90
Purchase #4	$170.83	5.298%	$179.8806	$179.88	$179.90	$179.90
Purchase #5	$83.56	9.299%	$91.3302	$91.33	$91.35	$91.30
Purchase #6	$62.85	3.485%	$65.0403	$65.04	$65.05	$65.00
Purchase #7	$243.36	7.858%	$262.4832	$262.48	$262.50	$262.50
7 purchase totals =	$1,063.16		$1,144.1461	$1,144.14	$1,144.25	$1,144.10