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	$162.58	6.377%	$172.9477	$172.95	$172.95	$172.90
Purchase #2	$79.63	8.477%	$86.3802	$86.38	$86.40	$86.40
Purchase #3	$20.65	4.549%	$21.5894	$21.59	$21.60	$21.60
Purchase #4	$7.84	8.441%	$8.5018	$8.50	$8.50	$8.50
Purchase #5	$127.27	3.557%	$131.797	$131.80	$131.80	$131.80
Purchase #6	$212.39	5.185%	$223.4024	$223.40	$223.40	$223.40
Purchase #7	$39.26	10.512%	$43.387	$43.39	$43.40	$43.40
7 purchase totals =	$649.62		$688.0055	$688.01	$688.05	$688.00