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	$223.63	11.495%	$249.3363	$249.34	$249.35	$249.30
Purchase #2	$119.94	6.161%	$127.3295	$127.33	$127.35	$127.30
Purchase #3	$185.28	5.816%	$196.0559	$196.06	$196.05	$196.10
Purchase #4	$69.82	9.591%	$76.5164	$76.52	$76.50	$76.50
Purchase #5	$242.46	8.144%	$262.2059	$262.21	$262.20	$262.20
Purchase #6	$161.80	4.132%	$168.4856	$168.49	$168.50	$168.50
Purchase #7	$103.45	4.430%	$108.0328	$108.03	$108.05	$108.00
7 purchase totals =	$1,106.38		$1,187.9624	$1,187.98	$1,188.00	$1,187.90