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	$95.47	3.836%	$99.1322	$99.13	$99.15	$99.10
Purchase #2	$129.75	10.174%	$142.9508	$142.95	$142.95	$143.00
Purchase #3	$193.65	5.630%	$204.5525	$204.55	$204.55	$204.60
Purchase #4	$49.26	10.775%	$54.5678	$54.57	$54.55	$54.60
Purchase #5	$190.61	3.165%	$196.6428	$196.64	$196.65	$196.60
Purchase #6	$65.81	6.218%	$69.9021	$69.90	$69.90	$69.90
Purchase #7	$134.99	3.541%	$139.77	$139.77	$139.75	$139.80
7 purchase totals =	$859.54		$907.5182	$907.51	$907.50	$907.60