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	$18.63	5.398%	$19.6356	$19.64	$19.65	$19.60
Purchase #2	$176.49	13.360%	$200.0691	$200.07	$200.05	$200.10
Purchase #3	$135.72	6.215%	$144.155	$144.16	$144.15	$144.20
Purchase #4	$239.52	7.271%	$256.9355	$256.94	$256.95	$256.90
Purchase #5	$180.76	9.855%	$198.5739	$198.57	$198.55	$198.60
Purchase #6	$220.96	13.290%	$250.3256	$250.33	$250.35	$250.30
Purchase #7	$113.64	5.250%	$119.6061	$119.61	$119.60	$119.60
7 purchase totals =	$1,085.72		$1,189.3008	$1,189.32	$1,189.30	$1,189.30