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	$53.54	8.223%	$57.9426	$57.94	$57.95	$57.90
Purchase #2	$249.99	4.555%	$261.377	$261.38	$261.40	$261.40
Purchase #3	$41.54	11.766%	$46.4276	$46.43	$46.45	$46.40
Purchase #4	$197.54	9.600%	$216.5038	$216.50	$216.50	$216.50
Purchase #5	$59.36	6.359%	$63.1347	$63.13	$63.15	$63.10
Purchase #6	$159.56	13.670%	$181.3719	$181.37	$181.35	$181.40
Purchase #7	$236.77	12.726%	$266.9014	$266.90	$266.90	$266.90
7 purchase totals =	$998.30		$1,093.6590	$1,093.65	$1,093.70	$1,093.60