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	$46.52	11.484%	$51.8624	$51.86	$51.85	$51.90
Purchase #2	$84.74	11.614%	$94.5817	$94.58	$94.60	$94.60
Purchase #3	$231.62	7.608%	$249.2416	$249.24	$249.25	$249.20
Purchase #4	$151.78	10.674%	$167.981	$167.98	$168.00	$168.00
Purchase #5	$120.42	6.197%	$127.8824	$127.88	$127.90	$127.90
Purchase #6	$239.96	3.162%	$247.5475	$247.55	$247.55	$247.50
Purchase #7	$150.43	13.416%	$170.6117	$170.61	$170.60	$170.60
7 purchase totals =	$1,025.47		$1,109.7083	$1,109.70	$1,109.75	$1,109.70