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	$64.84	10.500%	$71.6482	$71.65	$71.65	$71.60
Purchase #2	$221.51	6.788%	$236.5461	$236.55	$236.55	$236.50
Purchase #3	$139.35	11.455%	$155.3125	$155.31	$155.30	$155.30
Purchase #4	$109.36	7.603%	$117.6746	$117.67	$117.65	$117.70
Purchase #5	$151.42	8.398%	$164.1363	$164.14	$164.15	$164.10
Purchase #6	$65.52	3.539%	$67.8388	$67.84	$67.85	$67.80
Purchase #7	$143.37	5.850%	$151.7571	$151.76	$151.75	$151.80
7 purchase totals =	$895.37		$964.9136	$964.92	$964.90	$964.80