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	$52.26	8.837%	$56.8782	$56.88	$56.90	$56.90
Purchase #2	$151.99	12.774%	$171.4052	$171.41	$171.40	$171.40
Purchase #3	$40.54	6.405%	$43.1366	$43.14	$43.15	$43.10
Purchase #4	$5.29	3.443%	$5.4721	$5.47	$5.45	$5.50
Purchase #5	$241.31	11.860%	$269.9294	$269.93	$269.95	$269.90
Purchase #6	$249.37	10.443%	$275.4117	$275.41	$275.40	$275.40
Purchase #7	$225.87	7.330%	$242.4263	$242.43	$242.45	$242.40
7 purchase totals =	$966.63		$1,064.6595	$1,064.67	$1,064.70	$1,064.60