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	$188.48	10.447%	$208.1705	$208.17	$208.15	$208.20
Purchase #2	$79.29	4.470%	$82.8343	$82.83	$82.85	$82.80
Purchase #3	$36.28	4.612%	$37.9532	$37.95	$37.95	$38.00
Purchase #4	$179.93	3.794%	$186.7565	$186.76	$186.75	$186.80
Purchase #5	$35.99	12.715%	$40.5661	$40.57	$40.55	$40.60
Purchase #6	$112.40	3.759%	$116.6251	$116.63	$116.65	$116.60
Purchase #7	$231.79	12.507%	$260.78	$260.78	$260.80	$260.80
7 purchase totals =	$864.16		$933.6857	$933.69	$933.70	$933.80