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	$100.28	8.850%	$109.1548	$109.15	$109.15	$109.20
Purchase #2	$7.54	13.343%	$8.5461	$8.55	$8.55	$8.50
Purchase #3	$80.70	9.493%	$88.3609	$88.36	$88.35	$88.40
Purchase #4	$100.52	12.847%	$113.4338	$113.43	$113.45	$113.40
Purchase #5	$245.30	12.486%	$275.9282	$275.93	$275.95	$275.90
Purchase #6	$21.82	5.495%	$23.019	$23.02	$23.00	$23.00
Purchase #7	$176.67	11.192%	$196.4429	$196.44	$196.45	$196.40
7 purchase totals =	$732.83		$814.8857	$814.88	$814.90	$814.80