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	$141.48	12.329%	$158.9231	$158.92	$158.90	$158.90
Purchase #2	$120.30	8.248%	$130.2223	$130.22	$130.20	$130.20
Purchase #3	$115.98	5.512%	$122.3728	$122.37	$122.35	$122.40
Purchase #4	$138.33	3.142%	$142.6763	$142.68	$142.70	$142.70
Purchase #5	$81.83	10.144%	$90.1308	$90.13	$90.15	$90.10
Purchase #6	$208.64	8.359%	$226.0802	$226.08	$226.10	$226.10
Purchase #7	$208.83	6.575%	$222.5606	$222.56	$222.55	$222.60
7 purchase totals =	$1,015.39		$1,092.9661	$1,092.96	$1,092.95	$1,093.00