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	$138.55	6.553%	$147.6292	$147.63	$147.65	$147.60
Purchase #2	$159.44	5.718%	$168.5568	$168.56	$168.55	$168.60
Purchase #3	$168.28	11.597%	$187.7954	$187.80	$187.80	$187.80
Purchase #4	$95.94	5.134%	$100.8656	$100.87	$100.85	$100.90
Purchase #5	$168.99	10.254%	$186.3182	$186.32	$186.30	$186.30
Purchase #6	$157.33	11.802%	$175.8981	$175.90	$175.90	$175.90
Purchase #7	$174.35	5.205%	$183.4249	$183.42	$183.40	$183.40
7 purchase totals =	$1,062.88		$1,150.4882	$1,150.50	$1,150.45	$1,150.50