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	$167.32	3.162%	$172.6107	$172.61	$172.60	$172.60
Purchase #2	$46.31	7.824%	$49.9333	$49.93	$49.95	$49.90
Purchase #3	$36.93	13.416%	$41.8845	$41.88	$41.90	$41.90
Purchase #4	$204.88	12.483%	$230.4552	$230.46	$230.45	$230.50
Purchase #5	$179.87	11.706%	$200.9256	$200.93	$200.95	$200.90
Purchase #6	$148.65	13.561%	$168.8084	$168.81	$168.80	$168.80
Purchase #7	$188.77	13.140%	$213.5744	$213.57	$213.55	$213.60
7 purchase totals =	$972.73		$1,078.1921	$1,078.19	$1,078.20	$1,078.20