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	$116.75	9.271%	$127.5739	$127.57	$127.55	$127.60
Purchase #2	$69.30	6.147%	$73.5599	$73.56	$73.55	$73.60
Purchase #3	$202.61	12.611%	$228.1611	$228.16	$228.15	$228.20
Purchase #4	$229.61	13.685%	$261.0321	$261.03	$261.05	$261.00
Purchase #5	$137.70	4.643%	$144.0934	$144.09	$144.10	$144.10
Purchase #6	$139.40	6.121%	$147.9327	$147.93	$147.95	$147.90
Purchase #7	$175.40	8.400%	$190.1336	$190.13	$190.15	$190.10
7 purchase totals =	$1,070.77		$1,172.4867	$1,172.47	$1,172.50	$1,172.50