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	$74.85	3.462%	$77.4413	$77.44	$77.45	$77.40
Purchase #2	$86.43	13.675%	$98.2493	$98.25	$98.25	$98.20
Purchase #3	$98.94	12.692%	$111.4975	$111.50	$111.50	$111.50
Purchase #4	$80.93	10.503%	$89.4301	$89.43	$89.45	$89.40
Purchase #5	$100.88	7.621%	$108.5681	$108.57	$108.55	$108.60
Purchase #6	$193.67	5.319%	$203.9713	$203.97	$203.95	$204.00
Purchase #7	$63.77	11.704%	$71.2336	$71.23	$71.25	$71.20
7 purchase totals =	$699.47		$760.3912	$760.39	$760.40	$760.30