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	$127.91	11.104%	$142.1131	$142.11	$142.10	$142.10
Purchase #2	$77.61	7.192%	$83.1917	$83.19	$83.20	$83.20
Purchase #3	$82.47	9.254%	$90.1018	$90.10	$90.10	$90.10
Purchase #4	$124.91	13.365%	$141.6042	$141.60	$141.60	$141.60
Purchase #5	$205.60	3.620%	$213.0427	$213.04	$213.05	$213.00
Purchase #6	$96.45	8.157%	$104.3174	$104.32	$104.30	$104.30
Purchase #7	$116.93	3.550%	$121.081	$121.08	$121.10	$121.10
7 purchase totals =	$831.88		$895.4519	$895.44	$895.45	$895.40