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	$208.81	12.484%	$234.8778	$234.88	$234.90	$234.90
Purchase #2	$69.73	4.445%	$72.8295	$72.83	$72.85	$72.80
Purchase #3	$171.87	4.136%	$178.9785	$178.98	$179.00	$179.00
Purchase #4	$163.68	12.688%	$184.4477	$184.45	$184.45	$184.40
Purchase #5	$212.76	13.651%	$241.8039	$241.80	$241.80	$241.80
Purchase #6	$203.46	4.144%	$211.8914	$211.89	$211.90	$211.90
Purchase #7	$246.55	10.277%	$271.8879	$271.89	$271.90	$271.90
7 purchase totals =	$1,276.86		$1,396.7167	$1,396.72	$1,396.80	$1,396.70