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	$179.37	6.836%	$191.6317	$191.63	$191.65	$191.60
Purchase #2	$51.81	6.687%	$55.2745	$55.27	$55.25	$55.30
Purchase #3	$168.27	11.618%	$187.8196	$187.82	$187.80	$187.80
Purchase #4	$45.38	5.254%	$47.7643	$47.76	$47.75	$47.80
Purchase #5	$46.55	11.167%	$51.7482	$51.75	$51.75	$51.70
Purchase #6	$231.64	7.280%	$248.5034	$248.50	$248.50	$248.50
Purchase #7	$12.28	11.825%	$13.7321	$13.73	$13.75	$13.70
7 purchase totals =	$735.30		$796.4738	$796.46	$796.45	$796.40