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	$189.40	3.494%	$196.0176	$196.02	$196.00	$196.00
Purchase #2	$167.75	11.746%	$187.4539	$187.45	$187.45	$187.50
Purchase #3	$246.50	6.300%	$262.0295	$262.03	$262.05	$262.00
Purchase #4	$233.31	10.768%	$258.4328	$258.43	$258.45	$258.40
Purchase #5	$192.69	6.333%	$204.8931	$204.89	$204.90	$204.90
Purchase #6	$42.93	9.814%	$47.1432	$47.14	$47.15	$47.10
Purchase #7	$125.89	12.375%	$141.4689	$141.47	$141.45	$141.50
7 purchase totals =	$1,198.47		$1,297.4390	$1,297.43	$1,297.45	$1,297.40