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	$62.78	7.739%	$67.6385	$67.64	$67.65	$67.60
Purchase #2	$249.89	7.435%	$268.4693	$268.47	$268.45	$268.50
Purchase #3	$39.49	10.618%	$43.683	$43.68	$43.70	$43.70
Purchase #4	$155.98	12.779%	$175.9127	$175.91	$175.90	$175.90
Purchase #5	$245.75	13.132%	$278.0219	$278.02	$278.00	$278.00
Purchase #6	$38.72	3.121%	$39.9285	$39.93	$39.95	$39.90
Purchase #7	$112.39	13.730%	$127.8211	$127.82	$127.80	$127.80
7 purchase totals =	$905.00		$1,001.4750	$1,001.47	$1,001.45	$1,001.40