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	$195.64	4.146%	$203.7512	$203.75	$203.75	$203.80
Purchase #2	$50.33	12.221%	$56.4808	$56.48	$56.50	$56.50
Purchase #3	$199.48	8.244%	$215.9251	$215.93	$215.95	$215.90
Purchase #4	$66.46	9.653%	$72.8754	$72.88	$72.90	$72.90
Purchase #5	$135.84	3.738%	$140.9177	$140.92	$140.90	$140.90
Purchase #6	$101.59	9.689%	$111.4331	$111.43	$111.45	$111.40
Purchase #7	$133.39	3.503%	$138.0627	$138.06	$138.05	$138.10
7 purchase totals =	$882.73		$939.4460	$939.45	$939.50	$939.50