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	$186.86	5.687%	$197.4867	$197.49	$197.50	$197.50
Purchase #2	$12.98	10.364%	$14.3252	$14.33	$14.35	$14.30
Purchase #3	$10.96	11.855%	$12.2593	$12.26	$12.25	$12.30
Purchase #4	$249.41	12.380%	$280.287	$280.29	$280.30	$280.30
Purchase #5	$167.70	11.641%	$187.222	$187.22	$187.20	$187.20
Purchase #6	$141.26	10.614%	$156.2533	$156.25	$156.25	$156.30
Purchase #7	$86.48	4.179%	$90.094	$90.09	$90.10	$90.10
7 purchase totals =	$855.65		$937.9275	$937.93	$937.95	$938.00