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	$138.82	6.534%	$147.8905	$147.89	$147.90	$147.90
Purchase #2	$223.56	13.593%	$253.9485	$253.95	$253.95	$253.90
Purchase #3	$115.77	3.444%	$119.7571	$119.76	$119.75	$119.80
Purchase #4	$66.76	8.835%	$72.6582	$72.66	$72.65	$72.70
Purchase #5	$167.67	5.475%	$176.8499	$176.85	$176.85	$176.80
Purchase #6	$157.45	4.255%	$164.1495	$164.15	$164.15	$164.10
Purchase #7	$185.37	5.120%	$194.8609	$194.86	$194.85	$194.90
7 purchase totals =	$1,055.40		$1,130.1146	$1,130.12	$1,130.10	$1,130.10