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	$73.81	11.248%	$82.1121	$82.11	$82.10	$82.10
Purchase #2	$54.46	8.484%	$59.0804	$59.08	$59.10	$59.10
Purchase #3	$197.45	11.274%	$219.7105	$219.71	$219.70	$219.70
Purchase #4	$20.61	10.516%	$22.7773	$22.78	$22.80	$22.80
Purchase #5	$179.47	9.461%	$196.4497	$196.45	$196.45	$196.40
Purchase #6	$21.73	6.352%	$23.1103	$23.11	$23.10	$23.10
Purchase #7	$43.93	4.868%	$46.0685	$46.07	$46.05	$46.10
7 purchase totals =	$591.46		$649.3088	$649.31	$649.30	$649.30