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	$180.32	9.454%	$197.3675	$197.37	$197.35	$197.40
Purchase #2	$150.67	4.291%	$157.1352	$157.14	$157.15	$157.10
Purchase #3	$185.97	5.676%	$196.5257	$196.53	$196.55	$196.50
Purchase #4	$211.52	5.822%	$223.8347	$223.83	$223.85	$223.80
Purchase #5	$62.88	6.734%	$67.1143	$67.11	$67.10	$67.10
Purchase #6	$167.84	4.411%	$175.2434	$175.24	$175.25	$175.20
Purchase #7	$74.60	10.258%	$82.2525	$82.25	$82.25	$82.30
7 purchase totals =	$1,033.80		$1,099.4733	$1,099.47	$1,099.50	$1,099.40