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	$90.45	10.595%	$100.0332	$100.03	$100.05	$100.00
Purchase #2	$219.76	6.739%	$234.5696	$234.57	$234.55	$234.60
Purchase #3	$86.98	5.147%	$91.4569	$91.46	$91.45	$91.50
Purchase #4	$145.62	9.385%	$159.2864	$159.29	$159.30	$159.30
Purchase #5	$76.82	7.442%	$82.5369	$82.54	$82.55	$82.50
Purchase #6	$119.48	4.650%	$125.0358	$125.04	$125.05	$125.00
Purchase #7	$143.82	5.583%	$151.8495	$151.85	$151.85	$151.80
7 purchase totals =	$882.93		$944.7683	$944.78	$944.80	$944.70