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	$134.54	5.807%	$142.3527	$142.35	$142.35	$142.40
Purchase #2	$86.69	3.275%	$89.5291	$89.53	$89.55	$89.50
Purchase #3	$102.50	3.266%	$105.8477	$105.85	$105.85	$105.80
Purchase #4	$57.42	10.338%	$63.3561	$63.36	$63.35	$63.40
Purchase #5	$20.31	8.497%	$22.0357	$22.04	$22.05	$22.00
Purchase #6	$48.95	10.217%	$53.9512	$53.95	$53.95	$54.00
Purchase #7	$16.84	3.526%	$17.4338	$17.43	$17.45	$17.40
7 purchase totals =	$467.25		$494.5063	$494.51	$494.55	$494.50