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	$179.36	9.525%	$196.444	$196.44	$196.45	$196.40
Purchase #2	$173.49	12.217%	$194.6853	$194.69	$194.70	$194.70
Purchase #3	$241.97	12.201%	$271.4928	$271.49	$271.50	$271.50
Purchase #4	$16.40	6.219%	$17.4199	$17.42	$17.40	$17.40
Purchase #5	$32.84	12.756%	$37.0291	$37.03	$37.05	$37.00
Purchase #6	$147.32	11.493%	$164.2515	$164.25	$164.25	$164.30
Purchase #7	$72.29	13.436%	$82.0029	$82.00	$82.00	$82.00
7 purchase totals =	$863.67		$963.3255	$963.32	$963.35	$963.30