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	$172.77	3.610%	$179.007	$179.01	$179.00	$179.00
Purchase #2	$137.91	13.758%	$156.8837	$156.88	$156.90	$156.90
Purchase #3	$241.92	10.132%	$266.4313	$266.43	$266.45	$266.40
Purchase #4	$128.57	11.472%	$143.3196	$143.32	$143.30	$143.30
Purchase #5	$34.97	10.674%	$38.7027	$38.70	$38.70	$38.70
Purchase #6	$98.91	6.701%	$105.538	$105.54	$105.55	$105.50
Purchase #7	$203.43	10.673%	$225.1421	$225.14	$225.15	$225.10
7 purchase totals =	$1,018.48		$1,115.0244	$1,115.02	$1,115.05	$1,114.90