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	$146.58	8.767%	$159.4307	$159.43	$159.45	$159.40
Purchase #2	$5.59	5.625%	$5.9044	$5.90	$5.90	$5.90
Purchase #3	$164.35	6.844%	$175.5981	$175.60	$175.60	$175.60
Purchase #4	$56.98	13.828%	$64.8592	$64.86	$64.85	$64.90
Purchase #5	$183.43	7.331%	$196.8773	$196.88	$196.90	$196.90
Purchase #6	$161.52	6.456%	$171.9477	$171.95	$171.95	$171.90
Purchase #7	$137.98	13.582%	$156.7204	$156.72	$156.70	$156.70
7 purchase totals =	$856.43		$931.3378	$931.34	$931.35	$931.30