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	$38.34	12.360%	$43.0788	$43.08	$43.10	$43.10
Purchase #2	$44.89	6.627%	$47.8649	$47.86	$47.85	$47.90
Purchase #3	$176.64	6.171%	$187.5405	$187.54	$187.55	$187.50
Purchase #4	$142.27	8.860%	$154.8751	$154.88	$154.90	$154.90
Purchase #5	$151.74	9.107%	$165.559	$165.56	$165.55	$165.60
Purchase #6	$54.35	5.132%	$57.1392	$57.14	$57.15	$57.10
Purchase #7	$79.89	7.523%	$85.9001	$85.90	$85.90	$85.90
7 purchase totals =	$688.12		$741.9576	$741.96	$742.00	$742.00