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	$171.80	9.642%	$188.365	$188.37	$188.35	$188.40
Purchase #2	$173.84	3.138%	$179.2951	$179.30	$179.30	$179.30
Purchase #3	$82.92	4.853%	$86.9441	$86.94	$86.95	$86.90
Purchase #4	$25.96	8.474%	$28.1599	$28.16	$28.15	$28.20
Purchase #5	$226.85	6.517%	$241.6338	$241.63	$241.65	$241.60
Purchase #6	$40.78	4.177%	$42.4834	$42.48	$42.50	$42.50
Purchase #7	$240.51	7.405%	$258.3198	$258.32	$258.30	$258.30
7 purchase totals =	$962.66		$1,025.2011	$1,025.20	$1,025.20	$1,025.20