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	$129.34	3.448%	$133.7996	$133.80	$133.80	$133.80
Purchase #2	$180.68	3.424%	$186.8665	$186.87	$186.85	$186.90
Purchase #3	$98.80	12.805%	$111.4513	$111.45	$111.45	$111.50
Purchase #4	$172.67	4.545%	$180.5179	$180.52	$180.50	$180.50
Purchase #5	$202.54	10.753%	$224.3191	$224.32	$224.30	$224.30
Purchase #6	$181.94	10.201%	$200.4997	$200.50	$200.50	$200.50
Purchase #7	$8.85	10.359%	$9.7668	$9.77	$9.75	$9.80
7 purchase totals =	$974.82		$1,047.2209	$1,047.23	$1,047.15	$1,047.30