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	$87.64	10.240%	$96.6143	$96.61	$96.60	$96.60
Purchase #2	$222.64	3.739%	$230.9645	$230.96	$230.95	$231.00
Purchase #3	$91.89	11.803%	$102.7358	$102.74	$102.75	$102.70
Purchase #4	$155.50	7.297%	$166.8468	$166.85	$166.85	$166.80
Purchase #5	$194.53	12.592%	$219.0252	$219.03	$219.05	$219.00
Purchase #6	$142.85	5.331%	$150.4653	$150.47	$150.45	$150.50
Purchase #7	$171.34	6.379%	$182.2698	$182.27	$182.25	$182.30
7 purchase totals =	$1,066.39		$1,148.9217	$1,148.93	$1,148.90	$1,148.90