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	$217.76	5.418%	$229.5582	$229.56	$229.55	$229.60
Purchase #2	$80.65	7.681%	$86.8447	$86.84	$86.85	$86.80
Purchase #3	$29.87	9.536%	$32.7184	$32.72	$32.70	$32.70
Purchase #4	$133.78	6.814%	$142.8958	$142.90	$142.90	$142.90
Purchase #5	$214.86	11.819%	$240.2543	$240.25	$240.25	$240.30
Purchase #6	$146.34	7.513%	$157.3345	$157.33	$157.35	$157.30
Purchase #7	$77.86	10.802%	$86.2704	$86.27	$86.25	$86.30
7 purchase totals =	$901.12		$975.8763	$975.87	$975.85	$975.90