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	$203.80	4.252%	$212.4656	$212.47	$212.45	$212.50
Purchase #2	$78.94	8.781%	$85.8717	$85.87	$85.85	$85.90
Purchase #3	$86.66	3.519%	$89.7096	$89.71	$89.70	$89.70
Purchase #4	$54.29	12.675%	$61.1713	$61.17	$61.15	$61.20
Purchase #5	$74.43	6.678%	$79.4004	$79.40	$79.40	$79.40
Purchase #6	$133.69	5.119%	$140.5336	$140.53	$140.55	$140.50
Purchase #7	$203.94	5.859%	$215.8888	$215.89	$215.90	$215.90
7 purchase totals =	$835.75		$885.0410	$885.04	$885.00	$885.10