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	$164.88	4.639%	$172.5288	$172.53	$172.55	$172.50
Purchase #2	$77.49	8.373%	$83.9782	$83.98	$84.00	$84.00
Purchase #3	$160.77	13.375%	$182.273	$182.27	$182.25	$182.30
Purchase #4	$41.60	5.297%	$43.8036	$43.80	$43.80	$43.80
Purchase #5	$141.82	13.237%	$160.5927	$160.59	$160.60	$160.60
Purchase #6	$197.51	10.438%	$218.1261	$218.13	$218.15	$218.10
Purchase #7	$145.82	13.691%	$165.7842	$165.78	$165.80	$165.80
7 purchase totals =	$929.89		$1,027.0866	$1,027.08	$1,027.15	$1,027.10