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	$43.39	5.799%	$45.9062	$45.91	$45.90	$45.90
Purchase #2	$42.50	3.223%	$43.8698	$43.87	$43.85	$43.90
Purchase #3	$55.61	12.406%	$62.509	$62.51	$62.50	$62.50
Purchase #4	$200.33	12.457%	$225.2851	$225.29	$225.30	$225.30
Purchase #5	$57.45	12.122%	$64.4141	$64.41	$64.40	$64.40
Purchase #6	$22.38	8.410%	$24.2622	$24.26	$24.25	$24.30
Purchase #7	$218.83	6.790%	$233.6886	$233.69	$233.70	$233.70
7 purchase totals =	$640.49		$699.9350	$699.94	$699.90	$700.00