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	$40.81	7.258%	$43.772	$43.77	$43.75	$43.80
Purchase #2	$101.49	9.855%	$111.4918	$111.49	$111.50	$111.50
Purchase #3	$177.81	7.680%	$191.4658	$191.47	$191.45	$191.50
Purchase #4	$229.73	8.781%	$249.9026	$249.90	$249.90	$249.90
Purchase #5	$142.77	9.202%	$155.9077	$155.91	$155.90	$155.90
Purchase #6	$122.71	3.659%	$127.2	$127.20	$127.20	$127.20
Purchase #7	$22.32	9.381%	$24.4138	$24.41	$24.40	$24.40
7 purchase totals =	$837.64		$904.1537	$904.15	$904.10	$904.20