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	$184.96	10.614%	$204.5917	$204.59	$204.60	$204.60
Purchase #2	$93.36	13.436%	$105.9038	$105.90	$105.90	$105.90
Purchase #3	$205.77	5.525%	$217.1388	$217.14	$217.15	$217.10
Purchase #4	$52.69	5.730%	$55.7091	$55.71	$55.70	$55.70
Purchase #5	$242.61	9.596%	$265.8909	$265.89	$265.90	$265.90
Purchase #6	$92.38	11.295%	$102.8143	$102.81	$102.80	$102.80
Purchase #7	$171.37	5.866%	$181.4226	$181.42	$181.40	$181.40
7 purchase totals =	$1,043.14		$1,133.4712	$1,133.46	$1,133.45	$1,133.40