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	$77.32	10.314%	$85.2948	$85.29	$85.30	$85.30
Purchase #2	$80.35	13.438%	$91.1474	$91.15	$91.15	$91.10
Purchase #3	$218.51	9.751%	$239.8169	$239.82	$239.80	$239.80
Purchase #4	$63.88	12.794%	$72.0528	$72.05	$72.05	$72.10
Purchase #5	$24.46	12.746%	$27.5777	$27.58	$27.60	$27.60
Purchase #6	$133.55	11.454%	$148.8468	$148.85	$148.85	$148.80
Purchase #7	$89.44	8.169%	$96.7464	$96.75	$96.75	$96.70
7 purchase totals =	$687.51		$761.4828	$761.49	$761.50	$761.40