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	$63.98	10.816%	$70.9001	$70.90	$70.90	$70.90
Purchase #2	$118.80	3.547%	$123.0138	$123.01	$123.00	$123.00
Purchase #3	$91.31	9.177%	$99.6895	$99.69	$99.70	$99.70
Purchase #4	$216.57	8.572%	$235.1344	$235.13	$235.15	$235.10
Purchase #5	$191.53	7.274%	$205.4619	$205.46	$205.45	$205.50
Purchase #6	$224.43	12.190%	$251.788	$251.79	$251.80	$251.80
Purchase #7	$91.83	13.624%	$104.3409	$104.34	$104.35	$104.30
7 purchase totals =	$998.45		$1,090.3286	$1,090.32	$1,090.35	$1,090.30