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	$131.93	12.678%	$148.6561	$148.66	$148.65	$148.70
Purchase #2	$63.69	5.311%	$67.0726	$67.07	$67.05	$67.10
Purchase #3	$52.77	5.206%	$55.5172	$55.52	$55.50	$55.50
Purchase #4	$155.86	7.548%	$167.6243	$167.62	$167.60	$167.60
Purchase #5	$147.89	5.606%	$156.1807	$156.18	$156.20	$156.20
Purchase #6	$249.49	6.267%	$265.1255	$265.13	$265.15	$265.10
Purchase #7	$53.50	6.788%	$57.1316	$57.13	$57.15	$57.10
7 purchase totals =	$855.13		$917.3080	$917.31	$917.30	$917.30