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	$157.33	12.461%	$176.9349	$176.93	$176.95	$176.90
Purchase #2	$144.46	5.801%	$152.8401	$152.84	$152.85	$152.80
Purchase #3	$28.95	5.595%	$30.5698	$30.57	$30.55	$30.60
Purchase #4	$202.37	12.860%	$228.3948	$228.39	$228.40	$228.40
Purchase #5	$89.31	12.682%	$100.6363	$100.64	$100.65	$100.60
Purchase #6	$59.35	12.756%	$66.9207	$66.92	$66.90	$66.90
Purchase #7	$167.85	5.344%	$176.8199	$176.82	$176.80	$176.80
7 purchase totals =	$849.62		$933.1165	$933.11	$933.10	$933.00