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	$71.50	8.433%	$77.5296	$77.53	$77.55	$77.50
Purchase #2	$107.88	6.258%	$114.6311	$114.63	$114.65	$114.60
Purchase #3	$120.82	12.185%	$135.5419	$135.54	$135.55	$135.50
Purchase #4	$119.79	7.111%	$128.3083	$128.31	$128.30	$128.30
Purchase #5	$104.45	4.848%	$109.5137	$109.51	$109.50	$109.50
Purchase #6	$101.86	3.852%	$105.7836	$105.78	$105.80	$105.80
Purchase #7	$40.56	8.214%	$43.8916	$43.89	$43.90	$43.90
7 purchase totals =	$666.86		$715.1998	$715.19	$715.25	$715.10