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	$225.46	5.839%	$238.6246	$238.62	$238.60	$238.60
Purchase #2	$248.93	12.814%	$280.8279	$280.83	$280.85	$280.80
Purchase #3	$90.41	6.589%	$96.3671	$96.37	$96.35	$96.40
Purchase #4	$226.53	8.846%	$246.5688	$246.57	$246.55	$246.60
Purchase #5	$95.28	3.737%	$98.8406	$98.84	$98.85	$98.80
Purchase #6	$221.43	4.756%	$231.9612	$231.96	$231.95	$232.00
Purchase #7	$250.37	5.162%	$263.2941	$263.29	$263.30	$263.30
7 purchase totals =	$1,358.41		$1,456.4843	$1,456.48	$1,456.45	$1,456.50