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	$167.72	13.416%	$190.2213	$190.22	$190.20	$190.20
Purchase #2	$243.89	12.553%	$274.5055	$274.51	$274.50	$274.50
Purchase #3	$61.62	10.268%	$67.9471	$67.95	$67.95	$67.90
Purchase #4	$208.85	13.870%	$237.8175	$237.82	$237.80	$237.80
Purchase #5	$25.75	6.374%	$27.3913	$27.39	$27.40	$27.40
Purchase #6	$163.45	11.302%	$181.9231	$181.92	$181.90	$181.90
Purchase #7	$58.66	9.223%	$64.0702	$64.07	$64.05	$64.10
7 purchase totals =	$929.94		$1,043.8760	$1,043.88	$1,043.80	$1,043.80