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	$145.92	3.489%	$151.0111	$151.01	$151.00	$151.00
Purchase #2	$202.96	6.300%	$215.7465	$215.75	$215.75	$215.70
Purchase #3	$150.40	9.401%	$164.5391	$164.54	$164.55	$164.50
Purchase #4	$151.33	8.616%	$164.3686	$164.37	$164.35	$164.40
Purchase #5	$208.88	11.121%	$232.1095	$232.11	$232.10	$232.10
Purchase #6	$101.86	9.605%	$111.6437	$111.64	$111.65	$111.60
Purchase #7	$217.27	7.245%	$233.0112	$233.01	$233.00	$233.00
7 purchase totals =	$1,178.62		$1,272.4297	$1,272.43	$1,272.40	$1,272.30