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	$52.73	3.555%	$54.6046	$54.60	$54.60	$54.60
Purchase #2	$126.99	11.737%	$141.8948	$141.89	$141.90	$141.90
Purchase #3	$234.45	3.567%	$242.8128	$242.81	$242.80	$242.80
Purchase #4	$77.46	6.856%	$82.7707	$82.77	$82.75	$82.80
Purchase #5	$99.97	9.718%	$109.6851	$109.69	$109.70	$109.70
Purchase #6	$172.90	13.676%	$196.5458	$196.55	$196.55	$196.50
Purchase #7	$206.87	8.829%	$225.1346	$225.13	$225.15	$225.10
7 purchase totals =	$971.37		$1,053.4484	$1,053.44	$1,053.45	$1,053.40