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	$217.84	7.381%	$233.9188	$233.92	$233.90	$233.90
Purchase #2	$95.84	13.546%	$108.8225	$108.82	$108.80	$108.80
Purchase #3	$153.84	4.208%	$160.3136	$160.31	$160.30	$160.30
Purchase #4	$101.76	11.752%	$113.7188	$113.72	$113.70	$113.70
Purchase #5	$125.83	13.445%	$142.7478	$142.75	$142.75	$142.70
Purchase #6	$55.49	7.804%	$59.8204	$59.82	$59.80	$59.80
Purchase #7	$191.72	8.777%	$208.5473	$208.55	$208.55	$208.50
7 purchase totals =	$942.32		$1,027.8892	$1,027.89	$1,027.80	$1,027.70