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	$202.48	3.160%	$208.8784	$208.88	$208.90	$208.90
Purchase #2	$178.82	8.757%	$194.4793	$194.48	$194.50	$194.50
Purchase #3	$118.71	4.224%	$123.7243	$123.72	$123.70	$123.70
Purchase #4	$205.74	13.119%	$232.731	$232.73	$232.75	$232.70
Purchase #5	$71.71	9.553%	$78.5605	$78.56	$78.55	$78.60
Purchase #6	$236.44	6.253%	$251.2246	$251.22	$251.20	$251.20
Purchase #7	$74.74	10.570%	$82.64	$82.64	$82.65	$82.60
7 purchase totals =	$1,088.64		$1,172.2381	$1,172.23	$1,172.25	$1,172.20