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	$170.58	5.328%	$179.6685	$179.67	$179.65	$179.70
Purchase #2	$248.33	5.463%	$261.8963	$261.90	$261.90	$261.90
Purchase #3	$121.82	7.661%	$131.1526	$131.15	$131.15	$131.20
Purchase #4	$206.90	6.678%	$220.7168	$220.72	$220.70	$220.70
Purchase #5	$44.50	8.604%	$48.3288	$48.33	$48.35	$48.30
Purchase #6	$237.90	4.389%	$248.3414	$248.34	$248.35	$248.30
Purchase #7	$45.25	13.413%	$51.3194	$51.32	$51.30	$51.30
7 purchase totals =	$1,075.28		$1,141.4238	$1,141.43	$1,141.40	$1,141.40