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	$53.67	4.167%	$55.9064	$55.91	$55.90	$55.90
Purchase #2	$207.56	4.811%	$217.5457	$217.55	$217.55	$217.50
Purchase #3	$184.78	7.695%	$198.9988	$199.00	$199.00	$199.00
Purchase #4	$131.32	7.789%	$141.5485	$141.55	$141.55	$141.50
Purchase #5	$214.33	8.760%	$233.1053	$233.11	$233.10	$233.10
Purchase #6	$159.33	10.521%	$176.0931	$176.09	$176.10	$176.10
Purchase #7	$36.90	6.386%	$39.2564	$39.26	$39.25	$39.30
7 purchase totals =	$987.89		$1,062.4542	$1,062.47	$1,062.45	$1,062.40