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	$186.39	5.324%	$196.3134	$196.31	$196.30	$196.30
Purchase #2	$218.61	3.575%	$226.4253	$226.43	$226.45	$226.40
Purchase #3	$240.59	7.691%	$259.0938	$259.09	$259.10	$259.10
Purchase #4	$203.44	8.717%	$221.1739	$221.17	$221.15	$221.20
Purchase #5	$102.98	8.283%	$111.5098	$111.51	$111.50	$111.50
Purchase #6	$168.66	7.268%	$180.9182	$180.92	$180.90	$180.90
Purchase #7	$169.88	5.664%	$179.502	$179.50	$179.50	$179.50
7 purchase totals =	$1,290.55		$1,374.9364	$1,374.93	$1,374.90	$1,374.90