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	$121.58	10.173%	$133.9483	$133.95	$133.95	$133.90
Purchase #2	$230.95	4.515%	$241.3774	$241.38	$241.40	$241.40
Purchase #3	$76.90	11.725%	$85.9165	$85.92	$85.90	$85.90
Purchase #4	$22.76	11.214%	$25.3123	$25.31	$25.30	$25.30
Purchase #5	$83.60	7.438%	$89.8182	$89.82	$89.80	$89.80
Purchase #6	$13.55	11.352%	$15.0882	$15.09	$15.10	$15.10
Purchase #7	$39.44	10.157%	$43.4459	$43.45	$43.45	$43.40
7 purchase totals =	$588.78		$634.9068	$634.92	$634.90	$634.80