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	$59.69	13.781%	$67.9159	$67.92	$67.90	$67.90
Purchase #2	$238.30	4.105%	$248.0822	$248.08	$248.10	$248.10
Purchase #3	$234.72	6.371%	$249.674	$249.67	$249.65	$249.70
Purchase #4	$152.63	12.551%	$171.7866	$171.79	$171.80	$171.80
Purchase #5	$232.59	6.319%	$247.2874	$247.29	$247.30	$247.30
Purchase #6	$164.65	13.169%	$186.3328	$186.33	$186.35	$186.30
Purchase #7	$114.47	7.794%	$123.3918	$123.39	$123.40	$123.40
7 purchase totals =	$1,197.05		$1,294.4707	$1,294.47	$1,294.50	$1,294.50